## What changed
- Extend `ApprovalReviewContributor` with a `decide` hook that can allow an
action, return a synchronous review result, or hand the request to the user.
- Pass contributors the request's approval state and a callback bound to the
existing synchronous reviewer. Review results satisfy the review gate while
the host continues to enforce permissions.
- Add structured reasons for requesting a fresh Guardian review and select the
first contributor decision in registration order.
GitOrigin-RevId: ec84474b3fcbcf1027c8502aa1c2947c10149f9d