~x-ai/grok-latest → B (2:5)

Side B fixes real behavior bugs (empty private-room gardens no longer fall through to public content; thread_post_index is centralized as stable 0-based chrono indices with redact-safe rebuild semantics) and adds focused integration/browser regression tests. Side A is mostly reshuffle noise—renames, legacy moves, Cargo.lock, and scaffolding—with far less net correctness per line despite its size.