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>

test/helpers/touchfiles.ts

@@ -170,6 +170,7 @@ export const E2E_TOUCHFILES: Record<string, string[]> = {
 
   // Autoplan
   'autoplan-core':  ['autoplan/**', 'plan-ceo-review/**', 'plan-eng-review/**', 'plan-design-review/**'],
+  'autoplan-dual-voice': ['autoplan/**', 'codex/**', 'bin/gstack-codex-probe', 'scripts/resolvers/review.ts', 'scripts/resolvers/design.ts'],
 
   // Multi-provider benchmark adapters — live API smoke against real claude/codex/gemini CLIs
   'benchmark-providers-live': ['bin/gstack-model-benchmark', 'test/helpers/providers/**', 'test/helpers/benchmark-runner.ts', 'test/helpers/pricing.ts'],
@@ -318,6 +319,7 @@ export const E2E_TIERS: Record<string, 'gate' | 'periodic'> = {
 
   // Autoplan — periodic (not yet implemented)
   'autoplan-core': 'periodic',
+  'autoplan-dual-voice': 'periodic',
 
   // Multi-provider benchmark — periodic (requires external CLIs + auth, paid)
   'benchmark-providers-live': 'periodic',