openai/gpt-chat-latest → B (10:1)

Side B implements a substantive feed correctness fix by introducing a shared `rpc_feed` path that anchors implicit catch-up to durable ingest order instead of timestamps, preserves permission filtering, adds room metadata to `FeedPost`, and includes integration tests covering timestamp collisions, private-room visibility, and revoked access. Side A mainly adds a planning document plus a thin `RouteContext` wrapper and re-export without migrating call sites or changing runtime behavior, so its lasting project impact is much smaller.