review-cross-check

Verify new code review findings — this session's review or ones pasted from parallel agents — against a pull request's head, cross-check the confirmed ones against the PR's existing review feedback, and report which findings are new, which materially add to existing ones, and which are already covered or refuted. Use after reviewing a PR, or when asked to check findings against existing PR comments or drop findings reviewers already raised. Takes a PR number or URL. Does not perform the review, fix code, or post to the PR (review-post).