feat(workbench): extend TruncatedCell to trace edges and selection rails (#750)

Follow-up to #749, which deliberately scoped TruncatedCell to the
non-virtualized columnar tables and left trace edges + single-column
selection rails as-is. Wire it into those too so every truncated data
cell in the workbench has the same full-content reveal (popover +
copy + modal-for-long).

Component:
- Add `align` prop ("start" | "end"). `end` hugs the right edge and
  right-justifies the display, for right-aligned columns like the trace
  `to_stage` cell. Defaults to "start" (unchanged).

Wiring:
- Trace propagation edges: from_stage / to_stage (to_stage align=end).
- Trace pipeline stage rail: stage label + summary.
- Trace turns rail: prompt + surface excerpts.
- Runs rail: session_id. Replay rail: prompt excerpt. Packs rail:
  pack_id. CORE-Logos pack rail: pack_id. Logos alignment rail: edge
  (rich source→target display, plain-text value for copy/reveal).
- Contemplation run rail: run_id; stage-evidence ids.
- Demos rail: title; scenario trace hash.
- Proposal detail: replay-equivalence hash, evidence hashes;
  proposal chain provenance.

Two row elements that were real <button>s (trace stage rail,
contemplation run row) are converted to <div role="button"> with an
Enter/Space onKeyDown handler — the codebase's established selectable-row
pattern (ProposalTable, RowShell) — so nesting TruncatedCell's button
trigger is valid HTML rather than a button-in-button.

Intentionally left as-is (documented):
- RunsRoute TurnRefRow is an <a>/<Link> row; nesting an interactive
  trigger inside an anchor is invalid HTML. The surface excerpt is
  reachable by following the link.
- Digests everywhere keep DigestBadge (already copy + full-value title).
- Section headings (e.g. the trace stage-detail <h3>) are not data cells.

Evidence: workbench-ui `pnpm build` (tsc -b) green; full vitest suite
535 passed / 60 files, incl. a new align assertion on TruncatedCell.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

workbench-ui/src/app/contemplation/ContemplationRoute.tsx

@@ -8,6 +8,7 @@ import { Panel } from "../../design/components/Panel/Panel";
 import { SearchInput } from "../../design/components/SearchInput/SearchInput";
 import { SplitPane } from "../../design/components/SplitPane/SplitPane";
 import { StableJsonViewer } from "../../design/components/StableJsonViewer";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { EmptyState } from "../../design/components/states/EmptyState";
 import { ErrorState } from "../../design/components/states/ErrorState";
 import { LoadingState } from "../../design/components/states/LoadingState";
@@ -57,10 +58,17 @@ function RunRow({
   onSelect: () => void;
 }) {
   return (
-    <button
-      type="button"
+    <div
+      role="button"
+      tabIndex={0}
       aria-current={selected ? "true" : undefined}
       onClick={onSelect}
+      onKeyDown={(event) => {
+        if (event.key === "Enter" || event.key === " ") {
+          event.preventDefault();
+          onSelect();
+        }
+      }}
       className={`grid w-full grid-cols-[minmax(0,1fr)_auto] items-start gap-3 border-b border-[var(--color-border-subtle)] px-3 py-2 text-left transition-colors hover:bg-[var(--color-surface-inset)] focus-visible:outline focus-visible:outline-2 focus-visible:outline-inset focus-visible:outline-[var(--color-focus-ring)] ${
         selected
           ? "border-l-2 border-l-[var(--color-selected-border)] bg-[var(--color-selected-bg)] pl-[10px]"
@@ -68,8 +76,13 @@ function RunRow({
       }`}
     >
       <span className="min-w-0">
-        <span className="block truncate font-mono text-xs text-[var(--color-text-muted)]">
-          {run.run_id}
+        <span className="block min-w-0">
+          <TruncatedCell
+            value={run.run_id}
+            label="run id"
+            mono
+            className="text-xs text-[var(--color-text-muted)]"
+          />
         </span>
         <span className="mt-1 block text-sm text-[var(--color-text-primary)]">
           {run.prompt ?? "Prompt not recorded"}
@@ -82,7 +95,7 @@ function RunRow({
       <span className="justify-self-end text-xs text-[var(--color-text-secondary)]">
         {boolLabel(run.learning_arc_closed)}
       </span>
-    </button>
+    </div>
   );
 }
 
@@ -108,8 +121,13 @@ function StageEvidence({ scene }: { scene: ContemplationScene }) {
       {rows.map((row) => (
         <div key={row.label} className="contents">
           <dt className="text-[var(--color-text-secondary)]">{row.label}</dt>
-          <dd className="m-0 truncate font-mono text-[var(--color-text-primary)]" title={row.value}>
-            {row.value}
+          <dd className="m-0 min-w-0">
+            <TruncatedCell
+              value={row.value}
+              label={row.label}
+              mono
+              className="text-[var(--color-text-primary)]"
+            />
           </dd>
         </div>
       ))}

workbench-ui/src/app/demos/DemoTheaterRoute.tsx

@@ -8,6 +8,7 @@ import { DigestBadge } from "../../design/components/DigestBadge/DigestBadge";
 import { Button } from "../../design/components/primitives/Button";
 import { Panel } from "../../design/components/Panel/Panel";
 import { SearchInput } from "../../design/components/SearchInput/SearchInput";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { VirtualizedList } from "../../design/components/VirtualizedList/VirtualizedList";
 import { EmptyState } from "../../design/components/states/EmptyState";
 import { ErrorState } from "../../design/components/states/ErrorState";
@@ -63,9 +64,11 @@ function DemoRow({
             : "border-l-2 border-l-transparent pl-[10px]"
       }`}
     >
-      <span className="truncate text-sm font-semibold text-[var(--color-text-primary)]">
-        {demo.title}
-      </span>
+      <TruncatedCell
+        value={demo.title}
+        label="demo title"
+        className="text-sm font-semibold text-[var(--color-text-primary)]"
+      />
       <span className="font-mono text-xs text-[var(--color-text-muted)]">
         {demo.scenario_count} scenarios
       </span>
@@ -225,9 +228,12 @@ function ResultRow({ scenario }: { scenario: DemoScenarioRunResult }) {
         </p>
       ) : null}
       {scenario.trace_hash ? (
-        <code className="truncate font-mono text-xs text-[var(--color-text-muted)]">
-          {scenario.trace_hash}
-        </code>
+        <TruncatedCell
+          value={scenario.trace_hash}
+          label="trace hash"
+          mono
+          className="text-xs text-[var(--color-text-muted)]"
+        />
       ) : null}
       {scenario.problems.length > 0 ? (
         <ul className="m-0 grid list-none gap-1 p-0">

workbench-ui/src/app/logos/LogosAlignmentTab.tsx

@@ -1,6 +1,7 @@
 import { useMemo } from "react";
 import { DagViewer } from "../../design/components/Dag/Dag";
 import type { DagEdgeInput, DagNodeInput } from "../../design/components/Dag/layout";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import type { LogosAlignmentRow } from "../../types/api";
 
 // Read-only CORE-Logos alignment tab (LG-4). The trilingual resonance graph
@@ -70,9 +71,16 @@ function EdgeCard({
       }`}
     >
       <div className="flex items-center justify-between gap-2 font-mono text-xs text-[var(--color-text-primary)]">
-        <span className="truncate">
-          {row.source_id} <span aria-hidden className="text-[var(--color-text-muted)]">→</span> {row.target_id}
-        </span>
+        <TruncatedCell
+          value={`${row.source_id} → ${row.target_id}`}
+          display={
+            <>
+              {row.source_id}{" "}
+              <span aria-hidden className="text-[var(--color-text-muted)]">→</span> {row.target_id}
+            </>
+          }
+          label="alignment edge"
+        />
         <span className="text-[var(--color-text-secondary)]">{row.weight.toFixed(2)}</span>
       </div>
       <div className="flex flex-wrap items-center gap-x-2 gap-y-1 text-[11px] text-[var(--color-text-secondary)]">

workbench-ui/src/app/logos/LogosRoute.tsx

@@ -14,6 +14,7 @@ import { Panel } from "../../design/components/Panel/Panel";
 import { SplitPane } from "../../design/components/SplitPane/SplitPane";
 import { StableJsonViewer } from "../../design/components/StableJsonViewer";
 import { TabBar, type Tab } from "../../design/components/TabBar/TabBar";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { EmptyState } from "../../design/components/states/EmptyState";
 import { ErrorState } from "../../design/components/states/ErrorState";
 import { LoadingState } from "../../design/components/states/LoadingState";
@@ -165,8 +166,13 @@ function PackRow({
       }`}
     >
       <span className="min-w-0">
-        <span className="block truncate font-mono text-sm text-[var(--color-text-primary)]">
-          {pack.pack_id}
+        <span className="block min-w-0">
+          <TruncatedCell
+            value={pack.pack_id}
+            label="pack id"
+            mono
+            className="text-sm text-[var(--color-text-primary)]"
+          />
         </span>
         <span className="mt-1 flex flex-wrap items-center gap-2 text-xs text-[var(--color-text-secondary)]">
           <span>{roleLabel(pack.role)}</span>

workbench-ui/src/app/packs/PacksRoute.tsx

@@ -9,6 +9,7 @@ import { Panel } from "../../design/components/Panel/Panel";
 import { SearchInput } from "../../design/components/SearchInput/SearchInput";
 import { SplitPane } from "../../design/components/SplitPane/SplitPane";
 import { StableJsonViewer } from "../../design/components/StableJsonViewer";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { TabBar, type Tab } from "../../design/components/TabBar/TabBar";
 import { TreeView } from "../../design/components/TreeView/TreeView";
 import { VirtualizedList } from "../../design/components/VirtualizedList/VirtualizedList";
@@ -81,8 +82,13 @@ function PackRow({
       }`}
     >
       <span className="min-w-0">
-        <span className="block truncate text-sm text-[var(--color-text-primary)]">
-          {pack.pack_id}
+        <span className="block min-w-0">
+          <TruncatedCell
+            value={pack.pack_id}
+            label="pack id"
+            mono
+            className="text-sm text-[var(--color-text-primary)]"
+          />
         </span>
         <span className="mt-1 flex flex-wrap items-center gap-2 text-xs text-[var(--color-text-secondary)]">
           <span>{sourceLabel(pack.source)}</span>

workbench-ui/src/app/proposals/ProposalChainViewer.tsx

@@ -1,4 +1,5 @@
 import { StableJsonViewer } from "../../design/components/StableJsonViewer";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { DagViewer, type DagEdgeInput, type DagNodeInput } from "../../design/components/Dag";
 import type { ProposalDetail } from "../../types/api";
 import { chainRecords, isRecord, jsonSource, stringField } from "./proposalView";
@@ -68,9 +69,12 @@ export function ProposalChainViewer({ proposal }: { proposal: ProposalDetail })
                     {index + 1}. {nodeLabel(record, index)}
                   </span>
                   {provenance(record) ? (
-                    <span className="truncate text-xs text-[var(--color-text-muted)]">
-                      {provenance(record)}
-                    </span>
+                    <TruncatedCell
+                      value={provenance(record) as string}
+                      label="provenance"
+                      align="end"
+                      className="text-xs text-[var(--color-text-muted)]"
+                    />
                   ) : null}
                 </div>
                 <StableJsonViewer source={jsonSource(record)} />

workbench-ui/src/app/proposals/ProposalsRoute.tsx

@@ -8,6 +8,7 @@ import type { ProposalSummary, MathProposalDetail, ProposalState, DownstreamEffe
 import { Button } from "../../design/components/primitives/Button";
 import { EmptyState } from "../../design/components/states/EmptyState";
 import { SearchInput } from "../../design/components/SearchInput/SearchInput";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { useListNavigation } from "../../design/hooks/useListNavigation";
 import { ErrorState } from "../../design/components/states/ErrorState";
 import { LoadingState } from "../../design/components/states/LoadingState";
@@ -396,8 +397,13 @@ function MathProposalDetailView({
           </div>
           <div>
             <dt className="text-[var(--color-text-muted)]">Replay Equivalence Hash</dt>
-            <dd className="m-0 text-[var(--color-text-primary)] font-mono truncate mt-0.5" title={proposal.replay_equivalence_hash}>
-              {proposal.replay_equivalence_hash}
+            <dd className="m-0 mt-0.5 min-w-0">
+              <TruncatedCell
+                value={proposal.replay_equivalence_hash}
+                label="replay equivalence hash"
+                mono
+                className="text-[var(--color-text-primary)]"
+              />
             </dd>
           </div>
         </dl>
@@ -454,9 +460,14 @@ function MathProposalDetailView({
           {hashes.map((hash: string, i: number) => (
             <div key={i} className="flex items-center gap-2">
               <span className="text-xs text-[var(--color-text-muted)] font-mono">#{i + 1}</span>
-              <code className="bg-[var(--color-surface-inset)] px-2 py-1 rounded font-mono text-xs text-[var(--color-text-primary)] truncate flex-1">
-                {hash}
-              </code>
+              <span className="min-w-0 flex-1 rounded bg-[var(--color-surface-inset)] px-2 py-1">
+                <TruncatedCell
+                  value={hash}
+                  label={`evidence hash #${i + 1}`}
+                  mono
+                  className="text-xs text-[var(--color-text-primary)]"
+                />
+              </span>
             </div>
           ))}
         </div>

workbench-ui/src/app/replay/ReplayRoute.tsx

@@ -7,6 +7,7 @@ import { Panel } from "../../design/components/Panel/Panel";
 import { SearchInput } from "../../design/components/SearchInput/SearchInput";
 import { SplitPane } from "../../design/components/SplitPane/SplitPane";
 import { Timestamp } from "../../design/components/Timestamp/Timestamp";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { VirtualizedList } from "../../design/components/VirtualizedList/VirtualizedList";
 import { EmptyState } from "../../design/components/states/EmptyState";
 import { ErrorState } from "../../design/components/states/ErrorState";
@@ -75,8 +76,13 @@ function TurnRow({
         <span className="block text-xs text-[var(--color-text-secondary)]">
           <Timestamp iso={turn.timestamp} format="relative" />
         </span>
-        <span className="mt-1 block truncate text-sm text-[var(--color-text-primary)]">
-          {turn.prompt_excerpt || `Turn #${turn.turn_id}`}
+        <span className="mt-1 block min-w-0">
+          <TruncatedCell
+            value={turn.prompt_excerpt || `Turn #${turn.turn_id}`}
+            label="prompt"
+            wrap="pre-wrap"
+            className="text-sm text-[var(--color-text-primary)]"
+          />
         </span>
       </span>
       <span className="justify-self-end font-mono text-xs text-[var(--color-text-muted)]">

workbench-ui/src/app/runs/RunsRoute.tsx

@@ -11,6 +11,7 @@ import { SplitPane } from "../../design/components/SplitPane/SplitPane";
 import { StableJsonViewer } from "../../design/components/StableJsonViewer";
 import { TabBar, type Tab } from "../../design/components/TabBar/TabBar";
 import { Timestamp } from "../../design/components/Timestamp/Timestamp";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { VirtualizedList } from "../../design/components/VirtualizedList/VirtualizedList";
 import { Button } from "../../design/components/primitives/Button";
 import { EmptyState } from "../../design/components/states/EmptyState";
@@ -155,8 +156,13 @@ function RunRow({
         <span className="block text-sm text-[var(--color-text-primary)]">
           {sourceLabel(run.source)}
         </span>
-        <span className="mt-1 block truncate font-mono text-xs text-[var(--color-text-muted)]">
-          {run.session_id}
+        <span className="mt-1 block min-w-0">
+          <TruncatedCell
+            value={run.session_id}
+            label="session id"
+            mono
+            className="text-xs text-[var(--color-text-muted)]"
+          />
         </span>
         <span className="mt-1 flex items-center gap-2 text-xs text-[var(--color-text-secondary)]">
           <span>{run.turn_count} turns</span>

workbench-ui/src/app/trace/TraceRoute.tsx

@@ -19,6 +19,7 @@ import { SplitPane } from "../../design/components/SplitPane/SplitPane";
 import { StableJsonViewer } from "../../design/components/StableJsonViewer";
 import { TabBar, type Tab } from "../../design/components/TabBar/TabBar";
 import { Timestamp } from "../../design/components/Timestamp/Timestamp";
+import { TruncatedCell } from "../../design/components/TruncatedCell";
 import { VirtualizedList } from "../../design/components/VirtualizedList/VirtualizedList";
 import {
   EpistemicStateBadge,
@@ -212,7 +213,9 @@ function PipelineStageRail({
       {stages.map((stage, index) => {
         const selected = stage.stage_id === selectedStageId;
         return (
-          <button
+          <div
+            role="button"
+            tabIndex={0}
             aria-pressed={selected}
             className={`grid min-h-16 grid-cols-[2rem_minmax(0,1fr)] gap-2 rounded border px-2 py-2 text-left focus-visible:outline focus-visible:outline-2 focus-visible:outline-[var(--color-focus-ring)] ${
               selected
@@ -221,23 +224,36 @@ function PipelineStageRail({
             }`}
             key={stage.stage_id}
             onClick={() => onSelect(stage.stage_id)}
-            type="button"
+            onKeyDown={(event) => {
+              if (event.key === "Enter" || event.key === " ") {
+                event.preventDefault();
+                onSelect(stage.stage_id);
+              }
+            }}
           >
             <span className="font-mono text-xs text-[var(--color-text-muted)]">
               {String(index + 1).padStart(2, "0")}
             </span>
             <span className="min-w-0">
               <span className="flex items-center justify-between gap-2">
-                <span className="truncate font-mono text-xs font-semibold text-[var(--color-text-primary)]">
-                  {stage.label}
-                </span>
+                <TruncatedCell
+                  value={stage.label}
+                  label="stage"
+                  mono
+                  className="text-xs font-semibold text-[var(--color-text-primary)]"
+                />
                 <PipelineStageStatus status={stage.status} />
               </span>
-              <span className="mt-1 block truncate text-xs text-[var(--color-text-secondary)]">
-                {stage.summary}
+              <span className="mt-1 block min-w-0">
+                <TruncatedCell
+                  value={stage.summary}
+                  label="summary"
+                  wrap="pre-wrap"
+                  className="text-xs text-[var(--color-text-secondary)]"
+                />
               </span>
             </span>
-          </button>
+          </div>
         );
       })}
     </section>
@@ -259,11 +275,20 @@ function PipelineTransitionList({ record }: { record: CognitivePipelineRecord })
             className="grid grid-cols-[minmax(0,1fr)_auto_minmax(0,1fr)] items-center gap-2 rounded border border-[var(--color-border-subtle)] bg-[var(--color-surface-raised)] px-2 py-1 font-mono text-[11px]"
             key={`${edge.from_stage}:${edge.to_stage}`}
           >
-            <span className="truncate text-[var(--color-text-secondary)]">{edge.from_stage}</span>
+            <TruncatedCell
+              value={edge.from_stage}
+              label="from stage"
+              mono
+              className="text-[var(--color-text-secondary)]"
+            />
             <span className="text-[var(--color-text-muted)]">{edge.label ?? "propagate"}</span>
-            <span className="truncate text-right text-[var(--color-text-primary)]">
-              {edge.to_stage}
-            </span>
+            <TruncatedCell
+              value={edge.to_stage}
+              label="to stage"
+              mono
+              align="end"
+              className="text-[var(--color-text-primary)]"
+            />
           </li>
         ))}
       </ol>
@@ -563,11 +588,21 @@ function TraceRow({
         <span className="block text-xs text-[var(--color-text-secondary)]">
           <Timestamp iso={turn.timestamp} format="relative" />
         </span>
-        <span className="mt-1 block truncate text-sm text-[var(--color-text-primary)]">
-          {firstLine(turn.prompt_excerpt) || `Turn #${turn.turn_id}`}
+        <span className="mt-1 block min-w-0">
+          <TruncatedCell
+            value={firstLine(turn.prompt_excerpt) || `Turn #${turn.turn_id}`}
+            label="prompt"
+            wrap="pre-wrap"
+            className="text-sm text-[var(--color-text-primary)]"
+          />
         </span>
-        <span className="mt-1 block truncate text-xs text-[var(--color-text-muted)]">
-          {turn.surface_excerpt}
+        <span className="mt-1 block min-w-0">
+          <TruncatedCell
+            value={turn.surface_excerpt}
+            label="surface"
+            wrap="pre-wrap"
+            className="text-xs text-[var(--color-text-muted)]"
+          />
         </span>
       </span>
       <span className="justify-self-end">

workbench-ui/src/design/components/TruncatedCell/TruncatedCell.test.tsx

@@ -45,6 +45,12 @@ describe("TruncatedCell", () => {
     expect(screen.getByRole("dialog", { name: "source" })).toBeInTheDocument();
   });
 
+  it("right-justifies content when align is end", () => {
+    render(<TruncatedCell value="to_stage" label="to stage" align="end" />);
+    const display = screen.getByText("to_stage");
+    expect(display).toHaveClass("text-right");
+  });
+
   it("does not bubble clicks to a surrounding row handler", async () => {
     const onRowClick = vi.fn();
     render(

workbench-ui/src/design/components/TruncatedCell/TruncatedCell.tsx

@@ -44,6 +44,12 @@ export interface TruncatedCellProps {
   wrap?: "break-all" | "pre-wrap";
   /** Class applied to the inline display span. */
   className?: string;
+  /**
+   * Horizontal alignment of the cell content. `end` hugs the right edge (for
+   * right-aligned table columns) and right-justifies the display text.
+   * Defaults to `start`.
+   */
+  align?: "start" | "end";
 }
 
 function shouldOfferModal(value: string) {
@@ -94,6 +100,7 @@ export function TruncatedCell({
   mono,
   wrap = "break-all",
   className,
+  align = "start",
 }: TruncatedCellProps) {
   const [modalOpen, setModalOpen] = useState(false);
   const offerModal = shouldOfferModal(value);
@@ -101,8 +108,17 @@ export function TruncatedCell({
   const stop = (event: { stopPropagation: () => void }) => event.stopPropagation();
 
   return (
-    <span className={cn("group/cell flex min-w-0 items-center gap-1", mono && "font-mono")}>
-      <span className={cn("truncate", className)} title={value}>
+    <span
+      className={cn(
+        "group/cell flex min-w-0 items-center gap-1",
+        align === "end" && "justify-end",
+        mono && "font-mono",
+      )}
+    >
+      <span
+        className={cn("truncate", align === "end" && "text-right", className)}
+        title={value}
+      >
         {display ?? value}
       </span>
       <Popover.Root>