Task 1.2 (Req 1.3, 1.4).
- Mechanism gains origin, review_tier, pairs, shape, guard with defaults;
rows written before this spec load unchanged.
- MechanismStore.load folds the append-only log by id (latest row wins)
so a re-seeded shape carries every pair that taught it.
- append_from_pair writes origin=corpus rows with a deterministic id
derived from the shape key; corpus_mechanisms selects searchable rows.
Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG
