Fix Codex hook path so .codex-directory installs run the detector

The committed .codex/hooks.json hardcoded .agents/skills/impeccable/scripts/
hook.mjs. On a .codex-directory install the skill payload lives at .codex/
skills/..., so the guarded command ([ ! -f X ] || node X) found no file and
silently no-opped, leaving the design detector dead for those users.

Derive the hook payload path from the emitting provider's own configDir rather
than hardcoding .agents:

- buildCodexHooksManifest(skillDir) now builds `${skillDir}/skills/impeccable/
  scripts/hook.mjs`; hooksJsonFor threads each provider's configDir through. The
  Codex provider (configDir .codex) emits .codex/skills; the root sync and the
  self-consistent dist/codex bundle both point at their own payload.
- CLI installer: project-scope hook rewriting now derives the provider's own
  project-relative path instead of preserving the bundle token. The Codex bundle
  ships a .codex/skills command, but the CLI lays the skill at .agents/skills, so
  the installed .codex/hooks.json is rewritten to .agents/skills (Claude keeps
  its ${CLAUDE_PROJECT_DIR} token; global installs keep the absolute rewrite).

Per-provider hook payload path after the fix:

  Emission                              hook path
  dist/codex/.codex/hooks.json          .codex/skills/impeccable/scripts/hook.mjs
  root .codex/hooks.json (build sync)   .codex/skills/impeccable/scripts/hook.mjs
  CLI .agents (codex) project install   .agents/skills/impeccable/scripts/hook.mjs
  CLI .agents (codex) global install    <home>/.agents/skills/.../hook.mjs (abs)
  .claude / .cursor                     unchanged

Tests: extended hook-build (codex-dir -> .codex/skills, agents-dir -> .agents/
skills) and skills-cli (bundle ships .codex/skills, install rewrites to .agents/
skills). Regenerated tracked .codex/hooks.json via build:release.

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

scripts/build.js

@@ -400,7 +400,7 @@ function syncRootHookManifests(rootDir) {
   const synced = [];
   for (const config of Object.values(PROVIDERS)) {
     if (!config.emitHooks) continue;
-    const manifest = hooksJsonFor(config.emitHooks);
+    const manifest = hooksJsonFor(config.emitHooks, { configDir: config.configDir });
     if (!manifest) continue;
     const rel = config.hooksManifestRel || path.join('hooks', 'hooks.json');
     const dest = path.join(rootDir, config.configDir, rel);