fix: honor stop_hook_active in the stop-review-gate hook

[mittalpk]

Fixes #548.

Summary

When the review gate is enabled, main() in stop-review-gate-hook.mjs runs the stop-time Codex review and emits {"decision":"block"} on any non-ok outcome (no output, timeout, failure, invalid JSON) — without checking whether this invocation is already a forced retry.

Claude Code re-invokes Stop hooks with stop_hook_active: true after a block decision. Since this hook never checked that flag, a review that times out or errors would re-run and re-block on every retry, until the harness's forced-retry cap force-ends the turn — worst in exactly the cases where the gate is least useful (a broken/slow review blocking the session 9× before being overridden).

Fix

Skip the review and return cleanly when input.stop_hook_active is set, matching the fix the issue itself suggested:

if (input.stop_hook_active) {
  logNote(runningTaskNote);
  return;
}

The issue also flagged codex-companion.mjs's config.stopReviewGate branches as "worth auditing... for the same issue." I checked — those are only config get/set/report code (buildSetupReport, handleSetup), not the review-blocking logic itself, which lives solely in stop-review-gate-hook.mjs. Confirmed via grep -rl "decision.*block\|runStopReview\|stop_hook_active" across plugins/ that only this one file implements it, so no second file needs the fix.

Tests

Added a regression test that:

1. Enables the review gate and snapshots the fake Codex binary's appServerStarts counter.
2. Sends the Stop hook input with stop_hook_active: true.
3. Asserts the hook exits with empty stdout (no block decision) and that appServerStarts is unchanged — proving the review subprocess was never spawned a second time, not just that the output happened to look right.

Confirmed the test fails against the pre-fix code via git stash isolation, reproducing the exact stale block decision the issue describes (Codex stop-time review found issues that still need fixes...).

Verification

• npm test: 92/92 passed, no regressions.
• No lint config found in this repo (no .eslintrc*/eslint.config.*).
• npm run build (tsc) requires a live codex app-server generate-ts run to produce .generated/app-server-types, which needs an actual Codex CLI installation not available in this environment — this change touches no TypeScript files, so it's out of scope for this fix, but flagging honestly rather than silently skipping it.