- _ddl.py: table creation (conditional on pgvector/pg_trgm)
- _embeddings.py: EmbeddingMixin — pgvector checks, embed generation, backfill
- _facts.py: FactMixin — upsert, search (vector + ILIKE), delete, list, count
- _summary.py: SummaryMixin — get/set conversation summary
- _session_state.py: SessionStateMixin — extraction tracking per session
- store.py: reduced to ~60-line facade composing all mixins

No external API changes — MemoryStore remains the single interface.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>