fix: pre-landing review round — 8 auto-fixes + 8 accepted findings hardened

The ship review army (4 specialists + red-team + checklist, 29 findings)
produced 8 mechanical auto-fixes and 11 decisions; the accepted set:

- win32 slug parity completed: lib/bin-context.ts gains the remote-first
  outermost walk + degraded-cache self-heal the bash side got this wave —
  the two implementations now agree on the stray-marker live-bug shape,
  pinned by shared fixtures (multi-specialist 9/10 finding).
- probe honors the plan's bounded-read decision: 256KB prefix, extraction
  semantics mirrored from parseTranscriptJsonl so probe/prepare can never
  diverge on the same file (>1MB transcript test).
- policy normalize parity: bash normalize() now matches canonicalizeRemote
  on .git/-trailing and uppercase-.GIT shapes (7-shape corpus pinned two
  ways) — a deny for those shapes could previously slip the transcript gate.
- session-update reclaim is TOCTOU-safe (atomic mv-aside on both branches).
- settings-hook: unparseable settings.json errors instead of being replaced
  with {}; ensure-event keys on (event, source) so matcher changes update
  in place — never zero or two registrations.
- dot-only slug guard at both parse sites (hostile 'url = ..' can't escape
  projects/); enqueue tmp-file janitor (1h TTL, inside the drain lock);
  brain-sync .migrating never clobbered; drop-queue/status count .migrating;
  snapshot -o warning correct + surfaced in diff mode; version-bump test
  order-dependence removed; uninstall clears the advance stamp.

Deferred with record: slug heal-probe cost sentinel (P3 TODO), FF_OK
conflation (noted, misdiagnosis-only).

270 pass / 0 fail across the 10 touched suites.

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

bin/gstack-session-update

@@ -73,16 +73,23 @@ fi
     [ -f "$_hb" ] || _hb="$LOCK_DIR"
     [ -n "$(find "$_hb" -maxdepth 0 -mmin +$LOCK_TTL_MINUTES 2>/dev/null)" ]
   }
+  # Reclaim is TOCTOU-safe via atomic mv-aside: `rm -rf` then `mkdir` lets TWO
+  # contenders both judge the lock stale, both remove it, and both win the
+  # mkdir (one rm can land between the other's rm and mkdir). `mv` of the lock
+  # dir is atomic — exactly one contender's mv succeeds; the loser's mv fails
+  # (ENOENT) and it backs off. The winner reaps the moved-aside dir at leisure.
   if ! mkdir "$LOCK_DIR" 2>/dev/null; then
     if lock_is_expired; then
-      rm -rf "$LOCK_DIR" 2>/dev/null
+      mv "$LOCK_DIR" "$LOCK_DIR.reap.$$" 2>/dev/null || { log_entry "SKIP lock_contested"; exit 0; }
+      rm -rf "$LOCK_DIR.reap.$$" 2>/dev/null
       mkdir "$LOCK_DIR" 2>/dev/null || { log_entry "SKIP lock_contested"; exit 0; }
       log_entry "RECLAIMED lock_ttl_expired"
     elif [ -f "$LOCK_DIR/pid" ]; then
       LOCK_PID=$(cat "$LOCK_DIR/pid" 2>/dev/null || echo 0)
       if [ "$LOCK_PID" -gt 0 ] 2>/dev/null && ! kill -0 "$LOCK_PID" 2>/dev/null; then
-        # Stale lock — remove and re-acquire
-        rm -rf "$LOCK_DIR" 2>/dev/null
+        # Stale lock — mv aside atomically (see reclaim note above), re-acquire
+        mv "$LOCK_DIR" "$LOCK_DIR.reap.$$" 2>/dev/null || { log_entry "SKIP lock_contested"; exit 0; }
+        rm -rf "$LOCK_DIR.reap.$$" 2>/dev/null
         mkdir "$LOCK_DIR" 2>/dev/null || { log_entry "SKIP lock_contested"; exit 0; }
       else
         # Live holder — or an empty/non-numeric pidfile inside the TTL