openai/gpt-chat-latest → B (3:2)

Side B fixes a correctness issue in feed catch-up by anchoring implicit feeds to durable ingest order instead of timestamps, preventing missed posts when timestamps collide or move backwards, and filters results through permission checks to avoid leaking revoked private content. The patch also factors feed generation into a shared `rpc_feed` helper and adds targeted integration tests covering multi-user timestamp collisions and private-room visibility, whereas Side A is largely a broad API/identity refactor with behavior and representation changes rather than a focused correctness improvement.