Merge origin/main (v1.60.1.0) into garrytan/gstack-fix-wave

Semantic reconciliation with the parallel time-attack wave (#2264):
- careful: adopt main's anchored full-command whitelist (stricter — also
  catches comment-hiding), re-apply this wave's two hardenings on top
  (capital -[rR] in the flag cluster; exclude `(` and backtick from safe
  targets so $()/backtick substitution cannot ride the whitelist). Union
  of both waves' test batteries passes (main's test.each incl. comment
  case + this wave's substitution/capital-R/FP-pin cases).
- one-way-doors: main landed the singular noun unification (a2a447a1);
  keep this wave's superset (plural s? + --summary-stdin runtime wiring).
- gbrain-local-status: union of states — main's engine-locked (#2194,
  exit 124 PGLite lock) + this wave's thin-client (#2051). --is-ok keeps
  main's intent (engine-locked = STOP) and this wave's (thin-client =
  usable). Test harness unions both fake behaviors.
- sync-gbrain/setup-gbrain tmpls: both Step 1.5 branches kept; generated
  SKILL.md resolved via bun run gen:skill-docs (never hand-edited).
- VERSION/package.json -> 1.61.0.0 per bin/gstack-next-version (main took
  1.60.1.0; PR #2470 claims 1.60.2.0). CHANGELOG: wave entry renumbered
  1.61.0.0 on top of main's 1.60.1.0; careful/#2024 bullets updated to
  describe the delta vs current main. TODOS: union.

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

bin/gstack-gbrain-detect

@@ -18,7 +18,7 @@
  *     "gstack_brain_sync_mode": "off"|"artifacts-only"|"full",
  *     "gstack_brain_git": true|false,
  *     "gstack_artifacts_remote": "https://..." | "",
- *     "gbrain_local_status": "ok"|"no-cli"|"missing-config"|"broken-config"|"broken-db"|"timeout",
+ *     "gbrain_local_status": "ok"|"no-cli"|"missing-config"|"broken-config"|"broken-db"|"engine-locked"|"timeout"|"thin-client",
  *     "gbrain_pooler_mode": "transaction"|"session"|null
  *   }
  *