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-slug

@@ -224,6 +224,12 @@ if [[ -z "$SLUG" ]]; then
   if [[ -n "$REMOTE_URL" ]]; then
     RAW_SLUG=$(printf '%s' "${REMOTE_URL%.git}" | sed -E 's#.*[:/]([^/]+)/([^/]+)$#\1-\2#')
     SLUG=$(printf '%s' "$RAW_SLUG" | tr -cd 'a-zA-Z0-9._-')
+    # Dot-only / degenerate guard: a hostile origin like `url = ..` (git
+    # accepts it) passes sed unchanged and would become SLUG=".." — filing
+    # state one level ABOVE ~/.gstack/projects/. Reject empty/"."/".."/
+    # slash-bearing slugs and fall through to the basename fallback below.
+    # (tr -cd already deletes "/", so */* is belt-and-braces.)
+    case "$SLUG" in ""|.|..|*/*) SLUG="" ;; esac
   fi
 fi