Electric — New Feature End-to-End

End-to-end guide for adding a new synced feature with Electric and TanStack DB. Covers the full journey: design Postgres schema, set REPLICA IDENTITY FULL, define shape, create proxy route, set up TanStack DB collection with electricCollectionOptions, implement optimistic mutations with txid handshake (pg_current_xact_id, awaitTxId), and build live queries with useLiveQuery. Also covers migration from old ElectricSQL (electrify/db pattern does not exist), current API patterns (table as query param not path, handle not shape_id). Load when building a new feature from scratch.