docs: land capacity-study evidence and share the rank-map helper

Brings the durable artifacts of research/portfolio-capacity-rebalancing onto
main so the rationale for raising the count cap lives with the code that cites
it. The matrix runner, the research simulator hooks and the study's unit tests
are deliberately left behind; they remain at tag research/portfolio-capacity-final.

Corrects conclusions that were reached on EV per trade and are now superseded:
the findings doc's decisions 1 (keep cap 10) and 4 (run the risk-floor A/B) are
struck through and answered in a new correction section, and the research README
and phase-A matrix entries are updated to match. The frozen specification itself
is untouched -- its recorded SHA-256 f1e37783 still verifies.

effective-risk-floor-ab.md is retained but marked CLOSED/NEGATIVE: the study it
proposes is already answered by cap15 vs cash_unbounded (-0.753pp CAGR while
EV/trade rises), and its EV-based pass rule would have shipped it.

scripts/research_rankings.py replaces a fourth copy of the historical rank-map
helper; run_research_matrix, run_execution_recovery_matrix and
run_daily_reentry_matrix now share it. The shared version adds a duplicate
observation guard and a deterministic symbol tie-break the copies lacked.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/research/README.md

@@ -25,7 +25,7 @@ score, Structural S/R, the Gate Target Ladder, sentiment, fundamentals) is
 | 1.5× ATR initial stop | Real exit | Cuts losers fast |
 | 3× ATR trailing stop, 30-day max hold | Real exit | Best Sharpe of every exit tested |
 | Post-stop normal gate reset | Re-entry policy | Stop always closes; a later gate failure and subsequent fresh qualification define the next signal episode. The selected study arm reached Sharpe 1.77 / CAGR 48.3% at capacity 10; live scan-before-outcome timing is stricter (Sharpe 1.68 / CAGR 44.8% analogue). [Full study](post-stop-reentry.md) |
-| Max 10 concurrent positions, 1% risk per trade | Sizing | Cap never binds in practice |
+| Max **15** concurrent positions, 1% risk per trade | Sizing | Raised from 10 (2026-08-05) so the count cap never binds: +1.075pp CAGR paired, 51 paths better / 2 worse, drawdown unchanged. Cash plus the 20% notional cap saturates the book near 12. [Findings](portfolio-capacity-bracket-findings.md#correction-2026-08-05-ev-per-trade-was-the-wrong-lens) |
 | Structural S/R | Human-facing product context | Clean, capped zones for charts and alerts; not read by the scanner |
 | Gate Target Ladder | Screening machinery | Volume-free transient proposals preserve the production candidate set exactly; never an exit |
 
@@ -61,7 +61,7 @@ invites overfitting.
 |---|---|
 | ATR trail multiple {1.5–4.0} | **Keep 3.0** — ≤2.0 whipsaws out the right tail; ≥2.5 is a plateau |
 | Momentum lookback (6-1, 3-1, 12-7 Novy-Marx, composites) | **Keep residual 12-1** — the others have IC ≈ 0 or weaker t-stats |
-| Selection cutoff {70…90} × book size {10, 15, 20} | **Keep 80 × 10** — monotonically worse in both directions |
+| Selection cutoff {70…90} × book size {10, 15, 20} | **Keep cutoff 80; book size now 15** — the focused daily bracket found cap 15 worth +1.075pp CAGR (the weekly replay's contrary reading was EV-per-trade). Weekly rank replacement hurt. [Findings](portfolio-capacity-bracket-findings.md#correction-2026-08-05-ev-per-trade-was-the-wrong-lens) |
 | Position sizing (equal-weight, inverse-vol, risk-% sweep) | **Keep 1% fixed-fractional** |
 | Primary-target probability floor | **Keep 20%** — pruned lottery targets, 1,428 → 1,089 qualified, lifted Sharpe |
 | Primary-target R:R selector | **Keep 1.5** — target choice is intentionally independent of the later 2.0 activation floor |
@@ -146,6 +146,7 @@ knobs.
 | **Broader universe** | Composition changes factor signs (fip tug-of-war); vol-tilt on breadth is only a **directional hypothesis** (auth. −0.048 / t −1.36) | Any prod broaden must re-validate 80/20 tilt; offline research only; research.sqlite requires completion manifest |
 | **Forward paper-trade record** | The only true out-of-sample evidence the snapshot cannot give | Time; mark entries at actual near-close fill once ops ships |
 | **Better target model for clear-air names** | The return is demonstrably there (#2 wins on raw CAGR in *both* train and test); it's the *flat* 3× ATR target that makes it too expensive in risk | Needs a per-name model, not a constant k×ATR |
+| **Minimum effective-risk floor** | ⛔ CLOSED NEGATIVE, not run. The floor lifts EV/trade (+0.032) and PF (+0.073) *by deleting trades* — 11.4 fewer per path, never one more — and costs **−0.753pp CAGR**, −0.047 Sharpe, −0.051 Calmar | Do not run the A/B; its EV-based pass rule would have shipped it. [Withdrawn specification](effective-risk-floor-ab.md) / [findings](portfolio-capacity-bracket-findings.md#correction-2026-08-05-ev-per-trade-was-the-wrong-lens) |
 
 ---
 
@@ -197,4 +198,19 @@ qualification. The [daily re-entry matrix](post-stop-reentry.md) supports this
 for the current 10-position book, but not as a universal rule for other
 portfolio capacities.
 
+Capacity is closed **positive**: the count cap was raised 10 → 15 so it no longer
+binds, worth **+1.075pp CAGR** paired across 175 paths (51 better, 2 worse) at
+unchanged drawdown. Fifteen is headroom, not a target — cap15 peaked at 12 with
+zero full-book skips, so cash plus the 20% notional cap is the real ceiling.
+
+An earlier reading of this run concluded "keep cap 10, added only 0.0018 R/trade."
+That was **EV per trade**, which is the wrong metric for a treatment that changes
+trade *count*: flat EV/trade means the blocked entries were as good as the taken
+ones, so refusing them cost their whole contribution to return. Weekly
+current-rank replacement remains rejected (−0.043 EV R, 24% churn). The 0.5%
+effective-risk-floor A/B is **closed negative** without being run — it costs
+0.75pp of CAGR while raising EV/trade, and its frozen pass rule would have shipped
+it. See the [frozen specification](portfolio-capacity-bracket.md) and the
+[capacity findings](portfolio-capacity-bracket-findings.md#correction-2026-08-05-ev-per-trade-was-the-wrong-lens).
+
 The next real evidence is **forward**, not backward: the live paper-trade record.