verifying-attestors

Add and verify a rookery attestor's output contract with the testkit fixture + catalog gate system. Use when adding/migrating an attestor contract, recording a real-run fixture, promoting a declared contract to proven, or debugging a red catalog-verify gate. Activates for tasks mentioning output contract, attestor contract, detector.yaml contract block, testkit fixture, catalog-verify, catalog-verify-live, provenExempt, liveExempt, record.sh, or proven vs declared.