RQ2-P3: bridge-federated-pool mechanism instrument + synthetic tests + calibration gate

Build the funnelling-mechanism instrument for the RQ2-P3 follow-up: a new
`bridge-federated-pool` topology drawing each circuit's bridge from a finite
willing-bridge pool (size B) under Zipf willingness skew (alpha), so bridge
concentration genuinely varies as a manipulated IV. Defensive measurement only:
synthetic seeds, no engine, no traffic, no confirmatory record read.

- assembler.py: add `bridge-federated-pool` branch + zipf_weights/weighted_draw
  helpers; existing lead `bridge-federated` branch left untouched and
  bit-reproducible (fresh bridge per seed).
- battery.py: enumerate_rq2p3_cells() = B{2,4,8} x alpha{0,1,2} + anchor B=50,
  alpha=0 (separate fn; frozen 6-cell lead lattice unmutated).
- analysis/rq2p3_calibration.py: DRY synthetic-only §7 calibration gate; no
  confirmatory data read. confirm_load_rq2.py/confirm.py/stats.py unchanged.
- tests/test_sor_rq2p3_pool.py: 9 synthetic tests (helpers + pool reuse/variance
  + lead branch reproducibility).

Calibration gate RAN: items 3 (monotonicity) & 4 (entropy) PASS; items 1 & 2 do
NOT match their naive-funnel wording because the ratified posterior yields a MIX
(rho>0 across the whole sweep incl anchor rho=+0.838; B=1 -> H=2.54 bits HIGH) --
the note-unique-bridge-artifact.md prediction, surfaced early. HARD HOLD: no
confirmatory battery, no prereg freeze; NEEDS-OPERATOR banner raised for the §7
item-1/2 re-word decision. Lead prereg SHA f22331a72e... untouched; worktree-only.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OVERSEER-STATUS.md

@@ -1,5 +1,18 @@
 # OVERSEER-STATUS — sor-consent build agent
 
+> **NEEDS-OPERATOR (2026-07-21, RQ2-P3 mechanism instrument):** the `bridge-federated-pool`
+> instrument is BUILT + synthetic-tested (9 tests) + the §7 calibration gate was RUN. Items **3
+> (monotonicity) and 4 (entropy) PASS**; items **1 and 2 do NOT hold as their naive-funnel text is
+> worded** — because the *ratified* posterior mechanically yields a **MIX** (ρ>0), not the naive
+> funnel. Item-1 anchor B=50,α=0 gives ρ=**+0.838** (stdev 0.0198), NOT the ρ-undefined zero-variance
+> degeneracy §7 expected; item-2 B=1 gives concentration c=1.0 (✓) but H=**2.54 bits HIGH** vs the
+> fresh-bridge reference 0.0 bits, contradicting the "low H" gloss. Every ρ across the whole
+> B∈{2,4,8}×α∈{0,1,2} sweep is ≥0 (0.00→0.838): a robust mix everywhere. This is exactly
+> `docs/note-unique-bridge-artifact.md`'s prediction, surfaced early at calibration — NOT an
+> instrument bug. **STOPPED per rail:** no confirmatory RQ2-P3 battery, no prereg freeze. Operator
+> must decide: re-word `rq2p3-mechanism-prereg.md` §7 gate items 1–2 (naive→mechanical) before
+> freezing, or rule otherwise. Lead prereg SHA f22331a72e… UNTOUCHED; worktree-only.
+
 RQ2 RATIFIED (operator Andre, 2026-07-20, while blind) — observation-consistent-set + uniform-mass per-circuit posterior; docs/stage-05-rq2-posterior-clarification.md flipped PROPOSED→RATIFIED. Offline loader built + synthetic-tested. BLIND HOLD REMAINS: no real RQ2 result until the battery completes.
 
 
@@ -66,3 +79,6 @@ RQ2 RATIFIED (operator Andre, 2026-07-20, while blind) — observation-consisten
 - 2026-07-20 SS5 ADVERSARIAL REVIEW DONE + committed: docs/stage-08-adversarial-review.md — self red-team of the filled paper vs stage06-results.json (no new stat, no raw-data touch, prereg untouched). PASS on: number fidelity (every abstract/§5 figure matches JSON to precision), Holm arithmetic (7,6,5,4; only RQ1-P1+RQ2-P1 survive), spin/over-claim (no-leak framing, honest-negative equal-prominence, lab-scope disclaimers), blinding integrity (§5-6 filled once post-seal), method-substitution (bit-faithful --verify).
 - 1 DEFECT FOUND + FIXED (prose only, ZERO numbers changed): RQ1-P1's below-chance AUC was wrongly attributed to "the bridge padding stream flattening" — but assembler.py sets padding_applied=(bridge=="on+padding"), so the no-pad RQ1-P1 arm carries NO cover stream. Corrected docs/stage-06-analysis.md + paper §5.2/§6 to state it's an unexplained pooled-correlator artifact, explicitly NOT padding. Point/CI/gate/Holm untouched.
 - STEPPING STONES COMPLETE: SS1 executor ✅ SS2 battery+freeze ✅ SS3 §6 pass ✅ SS4 paper fill ✅ SS5 red-team ✅. Honest double-null/negative lead paper ready for operator review. prereg SHA INTACT; worktree-only feat/sor-consent-relay.
+- 2026-07-21 RQ2-P3 MECHANISM INSTRUMENT BUILT + committed: assembler.py `bridge-federated-pool` topology (finite willing-bridge pool size B under Zipf willingness skew α; per-circuit draw idx=weighted_draw(sha256("sor-bridge-pool|{seed}"), zipf_weights(B,α)) → bridge#{idx:02d}) + helpers `zipf_weights`/`weighted_draw`; existing lead `bridge-federated` branch UNTOUCHED (still fresh-bridge-per-seed, bit-reproducible). battery.enumerate_rq2p3_cells() = B∈{2,4,8}×α∈{0,1,2} + anchor B=50,α=0, tagged RQ2P3 (SEPARATE fn; frozen 6-cell lattice unmutated). analysis/rq2p3_calibration.py = DRY synthetic-only §7 gate (no confirmatory record read). confirm_load_rq2.py/confirm.py/stats.py UNCHANGED.
+- CALIBRATION GATE RAN (§7, DRY): item3 monotonicity PASS (top-3 conc ↓ in B, ↑ in α), item4 entropy PASS (plug-in=log2N exact). item1 + item2 DO NOT match naive wording → MIX not funnel (see top-of-file NEEDS-OPERATOR): anchor ρ=+0.838, B=1 H=2.54 bits HIGH, all 10 sweep ρ≥0. Surfaced, not reconciled. Tests: tests/test_sor_rq2p3_pool.py 9 passed; full SOR suite 185 passed (lead bridge-federated fingerprint reproducible — no regression).
+- HARD HOLD: no RQ2-P3 confirmatory battery, no `rq2p3-mechanism-prereg.md` freeze (§10 block still empty) — operator-gated on the item-1/2 re-word decision. Lead prereg SHA f22331a72e… INTACT; containment intact (synthetic-only, no engine/traffic); worktree-only. NEXT (operator-gated): RQ3 executor wiring, only after this ruling.