release: v0.18.4.0 — codex + Apple Silicon hardening wave

- Apple Silicon codesign fix (#1003 @voidborne-d)
- Codex stdin deadlock fix (#972 @loning)
- Codex timeout wrapper (gtimeout → timeout → unwrapped fallback)
- Multi-signal auth gate for /codex + /autoplan
- Codex version warning for known-bad CLI (0.120.0-0.120.2)
- Challenge mode stderr capture + completeness check
- Plan-review right-sized diff counterbalance
- Failure telemetry + auto-log timeout as operational learning
- 25 deterministic unit tests + dual-voice periodic E2E

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "0.18.3.0",
+  "version": "0.18.4.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",