~x-ai/grok-latest → B (2:3)

B fixes foundational feed catch-up by anchoring on durable ingest index (not wall-clock ts), so same-ms and clock-rollback posts are not skipped, and adds permission-aware multi-user private-room filtering plus room on FeedPost with strong integration tests. A’s real /- empty-index fix and GitHub card renderer matter, but much of that patch is resolver relocation/UI chrome versus B’s core correctness and leak-prevention design.