Phase 53: building-CV re-adjudication - GHOST_ZERO/QUARANTINE/combined all reject; screen confirms feature rejections; record closed

EXPERIMENTS.md

@@ -2777,3 +2777,47 @@ population before suspecting the delivery.
 
 Standing: local champion base 1661.7 (cert-first off), public champion
 **3c7b883 at 1661.45**. Deadline 2026-08-23.
+
+## Phase 53 - the user's re-adjudication directive: promising ideas vs the building-split CV
+
+Directive: retry the most promising rejected ideas against the new
+building-split instruments. Inventory first: everything from phases 41-51 had
+ALREADY faced a building-split instrument (the gate splits by building since
+phase 40), so the genuinely untested cells were the phase-15 ghost mechanisms
+(rejected pre-gate, on the native panel only) and the feature variants through
+the Phase-52 building screen column. Four parallel measurements, base
+reproduced at 1661.7 in every arm.
+
+| candidate | cost harness (ALL-48) | building gate | verdict |
+|---|---|---|---|
+| GHOST_ZERO | **+472.7** (10W/37L; late +573, early -109) | rec@20 0.866 -> **0.681**, -180 caught (4W/136L) | REJECT |
+| QUARANTINE | **+395.0 +/- 68.2** (13W/35L; late -189, early +539) | flat: -10/-6/-10/+4/-4, all noise | REJECT |
+| both | **+682.9** (9W/39L) | rec@20 -> 0.674, -187 caught | REJECT |
+| vcorr / zone / vrel | (native refs +32.7/+104.9/+138.7) | screen margins **negative at rec@12 in nearly every fold draw** | CONFIRMED REJECTED |
+
+Two mechanisms worth the record:
+
+- **GHOST_ZERO's mask is not ghost-specific.** days_below_245 is sticky, so
+  the zeroed pool GROWS across the walk (2-6 devices early, 33-42 by s_24+,
+  mean 22.4/scenario) and ~12% of it (128 devices over 48 scenarios) are real
+  in-window deaths - each becomes a guaranteed miss. The foreign-fleet hope is
+  quantified away: a target fleet would need a ghost-to-death ratio in the
+  below-2.45 pool far beyond anything the building split simulates before the
+  ~111-early-days-per-avoided-force-swap saving covers the misses.
+- **QUARANTINE's "label noise" is calibration ballast.** Dropping the
+  looks-dead-labeled-alive negatives barely changes ordering (p42 Spearman
+  0.9905 at s_20) but nearly DOUBLES the p42 level (0.0187 -> 0.0345): those
+  mislabeled rows are the only counter-evidence that plunge signatures can
+  survive, and removing them inflates every probability the count rule and
+  the ec-margin logic consume. Late improves (-189), early explodes (+539).
+
+The building screen column itself AGREED with the native cost harness on all
+three feature variants - tiny uniformly-positive AUC margins with negative
+operating-point recall, the familiar mid-list-reshuffle signature. The
+transfer-shaped fold offers no grounds to revisit anything.
+
+**The re-adjudication is complete and the record is now closed on every axis
+under the deployment-shaped instruments.** Champion 3c7b883 / current head
+(static @ 0.8, cert and pooling off) stands. Endgame per the user's mechanics
+(private = user-selected past versions): score the current head publicly; if
+~1661, select the head for private (robustness-hardened); else select 3c7b883.