Phase 48 submission: isolate cert-first (HELDOUT_POOL default off)

Public look spent on the phase-46 certainty-first ordering: rank_score =
2+p42 for devices whose gated daily median sustained <2.40 V for 3
consecutive gated readings, all confirmed <= origin. Local all-48 cost
1661.7 -> 1623.7, 3W/0L/45T; loss-free at every fixed N on both instruments;
fires 0.46 devices/scenario (the label-lag wobble population).

Pooling default flipped off per its public verdict (phase 42: 1665.89 vs
1661.45, 3x training deaths bought zero recall), so this submission is
cert-first against the 1661.45 champion with no confound.

Rehearsed on the 2x held-out fixture: static foreign fit both splits,
cert-first fired at 32 scenario-instances, 79560 rows in 162s, no fallbacks.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

batteryswap_example/submit.py

@@ -73,7 +73,10 @@ GRID_STEP_DAYS = 4
 # today. If the build overruns HELDOUT_BUILD_BUDGET_S we degrade to the plain
 # static foreign fit - i.e. to the CURRENT CHAMPION - and never to the pickle
 # fallback, which is far below it. Set HELDOUT_POOL=0 to disable.
-HELDOUT_POOL = os.environ.get('BATTERYSWAP_HELDOUT_POOL', '1') != '0'
+# Phase 42 PUBLIC verdict: pooling was a wash with the wrong sign (1665.89 vs
+# 1661.45; 3x training deaths bought zero recall). Default OFF so the phase-48
+# submission isolates cert-first; env re-enables for experiments.
+HELDOUT_POOL = os.environ.get('BATTERYSWAP_HELDOUT_POOL', '0') != '0'
 HELDOUT_GRID_STEP_DAYS = int(os.environ.get('BATTERYSWAP_HELDOUT_GRID', '16'))
 HELDOUT_BUILD_BUDGET_S = float(os.environ.get('BATTERYSWAP_HELDOUT_BUDGET_S', '360'))
 # Refit cadence. The rehearsal showed the table build is cheap (7s at grid 16d