Closes audit Finding 4 (2026-05-20) — Phase C1.
Pre-fix ``CognitiveTurnPipeline.run()`` called only the single-intent
``classify_intent`` and silently dropped every secondary clause of a
compound prompt like *"What is X and how does it relate to Y?"*.
The graph never saw the second subject, the resolver never saw the
second clause, and the trace recorded only the dominant clause —
with no operator-visible evidence that anything was dropped.
Phase C1 is the **observability substrate** for ADR-0089: the
pipeline now also runs ``classify_compound_intent`` at step 1b and
records every dropped secondary clause on
``CognitiveTurnResult.dropped_compound_clauses``. The dominant
clause continues to route through the existing single-intent path
exactly as before — surfaces, trace_hashes, and every existing test
remain byte-identical.
Changes:
* ``CognitiveTurnPipeline.run()`` calls ``classify_compound_intent``
alongside the existing ``classify_intent`` and computes
``dropped_compound_clauses = compound.parts[1:]`` when the
compound is multi-part.
* ``CognitiveTurnResult.dropped_compound_clauses:
tuple[DialogueIntent, ...] = ()`` — empty tuple == single-clause
turn; len > 0 == operator-visible evidence of dropped secondary
clauses.
Out of scope (per ADR-0089):
* Phase C2 (opt-in multi-node graph dispatch + widened trace_hash
+ multi-clause surface) is deliberately scoped to a separate
PR because it widens ``compute_trace_hash``, the surface
resolver contract, and ``plan_articulation``.
* The dominant-clause routing path is unchanged: the audit's
broken-subject case ("truth, and why does it matter") is *not*
fixed here — that improvement is Phase C2 scope.
Verification:
* 4 new tests in ``tests/test_compound_intent_substrate.py``:
- single-clause prompts record empty
``dropped_compound_clauses``
- AND-joined compound surfaces the secondary clause as a
DialogueIntent with the right tag (CAUSE for "why does ...")
- the user-visible surface and trace_hash for a compound prompt
are byte-identical across two independent runs (no behavior
change at the truth-path layer)
- prompts without a recognised connector do not invent a
secondary clause
* ``core eval cognition`` — public 100/100/91.7/100, byte-identical
to the MEMORY baseline.
* ``core test --suite cognition`` — 120/0/1.
* ``core test --suite smoke`` — 67/0.
* ``core test --suite runtime`` — 19/0.
