Add local Codex PR review script (ported from knowmarks)

[spaceshipmike]

What

Ports knowmarks' local Codex PR-review tool to setlist as scripts/codex_review.py.

It runs a local Codex review of a PR ($0, on the ChatGPT/Codex subscription — no API key), posts a structured verdict (APPROVE / REQUEST_CHANGES + severity-tagged findings) as a PR comment, and can squash-merge when Codex approves with no P1/P2 findings. The GitHub-hosted Check workflow verifies build/tests; this owns the correctness/logic review + merge.

Why this shape (setlist is public)

setlist is a public repo, so per ~/.claude/rules/self-hosted-ci-runner.md it intentionally stays GitHub-hosted for CI — knowmarks' self-hosted NAS runner and pr-pipeline.yml are deliberately not ported. This is the one piece that is safe and worth porting, because it runs on your Mac, never in CI.

All of knowmarks' hardening is preserved:

• author == OWNER gate — only ever reviews/merges your own PRs; a stranger's PR is rejected.
• Untrusted-worktree instruction stripping — removes AGENTS.md / codex.md / .codex from the reviewed worktree so a PR can't instruct its own approver (the diff still shows them as changes to scrutinize). CLAUDE.md is left alone — Codex doesn't load it.
• Fail-closed CI-green gate — requires the always-on changes gateway present-and-passing, so a pipeline that never ran can't read as green.
• Gate-self-modification guard — a PR touching this script or .github/workflows/ is never auto-merged.
• Head-SHA-pinned merge — refuses if the head moved since the review.

Usage

python3 scripts/codex_review.py <PR> [--dry-run] [--no-ci-check]

Requires gh (authenticated) and codex (logged in) on PATH. Stdlib only — no uv/venv.

First real run: reviewed #53 (--dry-run) → APPROVE, 0 findings.

Note: this PR adds a gate file, so by its own rules it will not auto-merge — it needs a human merge.

🤖 Generated with Claude Code

[spaceshipmike]

🤖 Codex review — APPROVE

Local Codex review of this PR's changes against origin/main.

Reviewed the PR diff and surrounding gate/CI context. The new local Codex review script is fail-closed on CI/query/review errors, strips PR-controlled Codex instruction files before review, pins the merge to the reviewed head SHA, and refuses auto-merge for gate-modifying PRs unless explicitly overridden. No blocking correctness or security issue found.

No issues found.