Crash self-report + round-completed latch + PDB archiving

CRASH SELF-REPORT (the #35/#41 heisenbug hunt): every unhandled
exception now logs its code, address, and an EBP-walked stack as
module-relative offsets (btl4+0xNNNN) into BT_LOG before dying --
any field crash on any machine hands us a resolvable stack.  The
walker is per-dereference guarded (a corrupt chain truncates).
BT_CRASHTEST=1 exercises the path end-to-end (verified: forced AV
logs code/addr/5-frame stack).  mkdist archives each build's PDB
next to its zip so offsets resolve per distributed version.

Context: a flaky release-only crash in the mech build path surfaced
during #38 rigs -- it moves with build layout, spares neither peer,
and masks under a debugger heap (13 clean cdb runs vs 2/3 crashes
without).  A real latent memory bug; the self-report will catch it
wherever it strikes next.

ROUND-COMPLETED LATCH (issue #38, awaiting verification): relay-mode
clients refuse RunMission after a round has ended -- the lobby-loop
relaunch owns the next round (in-process round 2 rebuilt every
player/mech entity on stale globals; matchlog caught player=3:1->3:36
in one generation).  Latch sets ONLY when the stop ends a RUNNING
mission (a stray pre-mission StopMission must not poison round 1 --
the first cut ate a legit launch, caught + fixed in rig).  Regression
verification pending (contaminated by the heisenbug above).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tools/mkdist.py

@@ -142,5 +142,15 @@ def main():
           % (len(bats) + len(exes) + len(tracked), total / 1048576.0,
              zsz / 1048576.0))
 
+    # Crash-forensics: archive this build's PDB next to the zip (operator-side
+    # only, never shipped) so the [crash] btl4+0xNNNN offsets in player logs
+    # stay resolvable per distributed version.
+    pdb = "build/Release/btl4.pdb"
+    if os.path.exists(pdb):
+        import shutil
+        pdb_dest = zpath[:-4] + ".pdb"
+        shutil.copyfile(pdb, pdb_dest)
+        print("  symbols archived: %s" % pdb_dest)
+
 if __name__ == "__main__":
     main()