#108 forensics block (pre-717): ghost detector + IDs + field envs

The night-11 instrumentation that makes the next ghost/K-D report
diagnosable instead of anecdotal:
- UNGATED [ghost] stale-replicant detector: ReadUpdateRecord stamps every
  applied record; the death-handler tick logs ONE line per starvation
  episode (>600 frames, unburied) with entity id + mode + last position,
  plus a GHOST matchlog record.  Verified both ways: zero false positives
  on a healthy 2-node session; fires on both nodes at frame 601 after a
  mid-session relay kill.
- Entity IDs on the render forensics (MakeMechRenderables / RemakeEntity /
  wreck-swap fallbacks) and the replicant un-wreck line un-gated -- ghost
  triage no longer needs players to set envs.
- players/*.bat (steam + both joins): BT_MATCHLOG/BT_SCORE_LOG/BT_DEATH_LOG
  on for every field session.

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

game/reconstructed/mech.cpp

@@ -2424,6 +2424,13 @@ Logical
 void
 	Mech::ReadUpdateRecord(Simulation::UpdateRecord *message)
 {
+	// #108 ghost forensics: stamp the staleness detector on every applied
+	// record (replicants only -- the detector lives on the death handler).
+	if (GetInstance() == ReplicantInstance)
+	{
+		extern void BTMechNoteUpdateApplied(void *mech_v);
+		BTMechNoteUpdateApplied((void *)this);
+	}
 	// RECORD-CADENCE probe (BT_RXJIT): quantify how EVENLY records arrive (wall-clock
 	// ms between arrivals) -- the jitter that makes the peer's corrections random.
 	if (getenv("BT_RXJIT") && GetInstance() == ReplicantInstance)