Review

Review and report only. Do not modify code, commit, push, merge, resolve review threads, or post GitHub comments unless the user explicitly asks for posting.

1. Establish the review target

Prefer, in order:

1. The PR base and head named by the user or .codex-review-context.json.
2. The current branch's PR from gh pr view.
3. Uncommitted and staged changes.
4. origin/main...HEAD for a committed branch.

Fetch only a missing base ref. If the diff is empty, stop. Record the exact base and head SHAs so a later force-push cannot silently change the target.