Fixed critical bugs affecting test suite:
**Clustering (2 tests fixed)**
- Fixed entity.type field reference bug in _getItemsByField()
- Changed entity.noun to entity.type (correct Entity interface field)
- Now includes ALL entities in domain clustering with 'unknown' fallback
**Relationship Metadata (5 tests fixed)**
- Fixed metadata retrieval in memoryStorage.ts getVerbs()
- Changed metadata.data to metadata.metadata for user's custom metadata
- User metadata now correctly returned in GraphVerb.metadata field
**Delete Relationship Cleanup (2 tests fixed)**
- Added deleteVerbMetadata() method to BaseStorage
- Fixed deleteVerb_internal() in memoryStorage to delete verb metadata
- Relationships now properly cleaned up when entities are deleted
**Validation (1 test fixed)**
- Removed overly restrictive self-referential relationship check
- Self-relationships now allowed (valid in graph systems)
Test results: 27 failures → 17 failures (37% improvement)
All 467 tests now enabled (0 skipped)
