Binding ADR for Phase 2 Postgres backend integration plus the Phase 1
amendment that removes async_trait from the storage and embedder traits.
Decisions D1-D8:
- D1: sunset async_trait across MemoryStore + Embedder via trait_variant
- D2: PgMemoryStore::connect(url, max_connections) mirrors SqliteMemoryStore;
no Embedder in constructor; register_model handles pgvector typmod
- D3: split sqlite.rs into a sqlite/ directory as Phase 1 amendment
- D4: postgres/ as a directory from day one
- D5: sub-plan layout -- 3 Phase 1 amendment + 9 Phase 2 sub-plans
- D6: no separate ADR for the SQLite split (pure code motion)
- D7: reserve multi-tenancy schema (users/groups/group_memberships +
owner_user_id/visibility/shared_with_groups) in Phase 2 so Phase 3 auth
is additive, not an online migration over an HNSW-indexed table
- D8: codebase promoted to a first-class indexed column on knowledge_nodes;
mcp_client_id and session_id stay in metadata JSONB
PR cadence: PR A = Phase 1 amendment (code on feat/storage-trait-phase1);
PR B = this ADR + Phase 2 sub-plans (docs only); PR C = Phase 2
implementation. Phase 4 sharing_rules table sketched in Follow-ups.
