Phase 13: gap/heat/room-cascade plunger hypotheses all rejected by panel

EXPERIMENTS.md

@@ -436,6 +436,31 @@ fleet. The building death-rate signal is real but weak exactly where the
 misses live, and largely confounded with install batch (~90% of lifetime
 variance, phase 6).
 
+## Phase 13 - plunger mechanism hypotheses: gaps, heat, room cascade (all rejected)
+
+Three user hypotheses for what precedes a fast plunge, each built leak-free
+per (device, origin) over all 168 origins and screened on the blind zone
+(11,599 healthy-voltage pairs / 24 silent deaths), then panel-adjudicated:
+
+| hypothesis | features | blind AUC | panel (champ 1702.0) | sel% |
+|---|---|---|---|---|
+| telemetry gaps precede death | gap_max_90 / gap_frac_90 / gap_trend | 0.42 / 0.34 / 0.59 - INVERTED: plungers report MORE cleanly than survivors | 1875.0 | 0.0% |
+| hot-running or temp spikes | temp_mean_life / temp_rise_30 / tmax30_rel / temp_hot_frac_90 | 0.68 / 0.42 / 0.39 / 0.49 - only lifetime heat mildly ages (phase-6 confirmed); recent temp is INVERTED | 1988.0 | 0.1% |
+| room cascade (peer fails -> room heats -> I fail) | room_death_90 / bldg_death_90 / room_peer_temp_rise_30 | 0.54 / 0.52 / 0.37 - peers' temp FALLS before a death, recent peer deaths ~chance | 1871.8 | 0.1% |
+
+Champion selected in 99.8% of random and 95% of blocked splits. Even the gap
+family's small additive screen nudge (rng_30 0.843 -> 0.867) becomes +173 in
+CV - three noisy features degrade p42 calibration, and the count rule turns
+that into worse inclusion counts.
+
+Mechanism picture after phases 6-13: the fast plunger runs slightly COOLER
+than its own baseline, spikes less, reports cleanly, and shows no
+environmental or neighbourhood stress - but its voltage wobbles (rng_30
+0.833, the one real precursor, itself unactionable at 0.2% prevalence). This
+is the signature of an internal cell failure, not an external stressor:
+nothing in temperature, telemetry health, or spatial context flags it before
+the plunge starts.
+
 ## Test-look ledger
 
 8 looks total (now historical - see protocol change above); look 9 = the