memory isolation fix and session grouping in client

docs/services/memory-service.md

@@ -180,7 +180,8 @@ After extraction, each entity is:
    the entity is new (`COALESCE(entities.notes, excluded.notes)` prevents
    overwriting existing notes with speculative updates)
 2. Embedded via the embedding service and upserted into the `entities`
-   Qdrant collection with `{ name, type, notes }` as payload
+   Qdrant collection with `{ name, type, notes, projectId }` as payload —
+   `projectId` scopes entities to their project for isolated retrieval
 
 The Qdrant payload stores enough information to reconstruct entity context
 at retrieval time without a SQLite roundtrip.