Task 4.1 (Req 5.1, 5.2, 5.5).
- validator: MechanismEdit (admit | retract by record id) under the
`mechanisms` lever; validate_mechanism accepts only records from the
exporter candidate set with origin corpus, a closed guard and source
kinds, and identifier-only shape text; free-form shapes are rejected.
- apply_mechanism_edits appends the record (admit) or a retracted
tombstone (retract) so the log stays append-only; StoreSnapshot.restore
reverts byte for byte. MechanismStore.load folds tombstones away.
Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG
