docs(math-reader): Phase 4.1 measured status — seeding injection is built, converts 0 (null result)

Re-measured the frozen holdout_dev/v1 500: correct=5 wrong=0 refused=495 —
exactly the tune-3 + measure-2 increment 1 recorded, no drift, wrong=0 held.

Seeding-sentence injection is already in the tree (NEUTRAL_COUNT_VERBS in
math_roundtrip.py, consumed by the seed matcher and the comparison anchor);
its measured yield when it shipped was 0 conversions, verified four ways.
Extending the allowlist further is the move ADR-0251 and the overfit
inventory forbid — per-case pattern growth previously produced lift that
committed WRONG answers on the real exam.

Recommendation: mark Phase 4.1 complete-with-null-yield and re-point Phase 4
at the reader arc's own live recommendation — increment-2 CASE-FIRST on the
already-identified closest cases (0000/0001/0148/0082).

docs/research/math-reader-phase-4-1-status-2026-07-24.md

@@ -0,0 +1,85 @@
+# Math reader Phase 4.1 — measured status: the increment is already built, and it converts nothing
+
+**Date:** 2026-07-24 · **Arc:** generalization Phase 4.1 (Tier O, O4) · **Result:** null, by measurement
+
+## What was asked
+
+The generalization plan §2/Phase 4.1 and the Opus brief item O4 both name
+"seeding-sentence injection (standing ruling #77 — the 75% 'no injection'
+wall)" as the next math move, with wrong=0 on the full 500 as the gate and
+parse-rate gain as the goal.
+
+## What is actually in the tree
+
+Seeding-sentence injection **is built and merged**. The reader arc's increment
+1 shipped it as the #78 positive-polarity substrate:
+
+- `generate/math_roundtrip.py::NEUTRAL_COUNT_VERBS` — the curated
+  production/possession/acquisition allowlist,
+- consumed by the seed matcher's `inject_discrete_count_statement` path and by
+  `generate/math_candidate_parser.py::_COMPARISON_ANCHOR_VERBS`,
+- depletion/transfer verbs refuse by positive determination (an allowlist, not
+  a blocklist — the fail-open blocklist was reverted),
+- documented in `docs/research/increment-1-band-plan-2026-07-19.md` §BUILD
+  OUTCOME.
+
+Its measured yield when it shipped: **PARSED unchanged — tune 3, measure 2, no
+conversion.** The scoped band `{seed + forward-comparison + q:simple/summation}`
+converted **0** tune cases, measured four independent ways (yield harness, band
+map, band oracle, capability histogram).
+
+## Re-measured today, on the frozen split
+
+```
+uv run python evals/gsm8k_math/holdout_dev/v1/runner.py
+holdout_dev: correct=5 wrong=0 refused=495 (n=500)
+```
+
+Five correct is exactly the tune-3 + measure-2 the increment-1 report recorded.
+**No drift in five days of unrelated arc work, and wrong=0 still holds.** The
+tune/measure split (`evals/gsm8k_math/holdout_dev/v1/split.py`) is frozen and
+was not touched.
+
+## Why the honest move is to stop rather than extend
+
+The arc's own evidence says the wall is not where 4.1 aims:
+
+1. **The ~30-band bet was falsified.** In-band cases strand on capabilities
+   *outside* the band — 25 need multi-compound, 17 need compare-additive.
+   Adding more seed verbs cannot convert a case that also needs rate,
+   currency, and unit conversion in the same sentence.
+2. **The taxonomy is not at bedrock.** The "smallest tractable set"
+   `{seed, q:simple}` dissolved on inspection: every one of its four cases
+   really needs rate / compare / currency / copula. Real GSM8K statements are
+   individually multi-capability — the conjunction recurs *within* a sentence,
+   so a capability list keeps fragmenting rather than converging.
+3. **Growing the allowlist is the forbidden move.** ADR-0251 and
+   `docs/research/reader-arc-overfit-inventory-2026-07-19.md` exist because
+   per-case pattern growth previously produced overfit "lift" that committed
+   *wrong* answers on the real exam. An extension whose only evidence is "it
+   parses more tune cases" is the exact shape of that failure.
+
+## The live next move (unchanged, and it is not 4.1)
+
+The reader arc's own recommendation, carried to Shay with the increment-1
+foundations, is **case-first, not capability-first**: pick 2–3 specific closest
+tune cases, hand-enumerate their *exact* end-to-end needs however many
+capabilities that is, build precisely that, convert them, measure. The closest
+cases are already identified — `0000`, `0001`, `0148`, `0082` — all needing
+complex compare forms (chained / mass-noun entities / "than" + aggregate
+reference) plus summation or difference.
+
+`multi-compound` is the single highest-leverage capability (on the critical
+path for 70/106 = 66% of tractable needed-sets) but is insufficient alone.
+`q:complex` remains the largest intractable wall (~35+ cases).
+
+## Recommendation for the plan
+
+Phase 4.1 should be marked **complete-with-null-yield** rather than pending,
+and Phase 4 re-pointed at the increment-2 case-first work. The measurement
+above is the evidence; nothing in this session's arc work moved it either way,
+which is itself the useful signal — the math lane is genuinely orthogonal to
+the reading/curriculum work, exactly as the plan's §3 dependency table assumed.
+
+Phase 4.2 (compare unblock) and 4.3 (q:complex decomposition study) are
+untouched by this and remain queued behind the case-first increment.