merge: integrate origin/main (v0.18.4.0) — codex + Apple Silicon hardening

Resolves conflicts in VERSION (kept 0.19.0.0), package.json (kept 0.19.0.0),
and CHANGELOG.md (preserved 0.19.0.0 at top, inserted 0.18.4.0 below).

Main brought v0.18.4.0's codex + Apple Silicon hardening wave (PR #1056):
- Apple Silicon ad-hoc codesigning in ./setup (fixes SIGKILL on first run)
- /codex stdin deadlock fix (redirect from /dev/null)
- /codex + /autoplan preflight auth + version checks
- 10-minute timeout wrapper via gtimeout/timeout
- New bin/gstack-codex-probe consolidates auth/version/timeout logic
- test/codex-hardening.test.ts (25 unit tests, gate tier)
- test/setup-codesign.test.ts
- test/skill-e2e-autoplan-dual-voice.test.ts (periodic tier)

Auto-merged SKILL.md.tmpl updates across autoplan, codex, plan-ceo-review,
plan-eng-review, and the scripts/resolvers/{design,review}.ts modules.
None conflicted with v0.19's preamble refactor or new benchmark-models
skill — clean 3-way merge.

Regenerated all SKILL.md files. Ship golden fixtures refreshed for
claude/codex/factory hosts. 423 tests pass.

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

design-consultation/SKILL.md

@@ -954,7 +954,7 @@ codex exec "Given this product context, propose a complete design direction:
 - Differentiation: 2 deliberate departures from category norms
 - Anti-slop: no purple gradients, no 3-column icon grids, no centered everything, no decorative blobs
 
-Be opinionated. Be specific. Do not hedge. This is YOUR design direction — own it." -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="medium"' --enable web_search_cached 2>"$TMPERR_DESIGN"
+Be opinionated. Be specific. Do not hedge. This is YOUR design direction — own it." -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="medium"' --enable web_search_cached < /dev/null 2>"$TMPERR_DESIGN"
 ```
 Use a 5-minute timeout (`timeout: 300000`). After the command completes, read stderr:
 ```bash