~x-ai/grok-latest → B (1:3)

B adds a real CLI `room create` path and simplifies the domain by dropping ThreadVisibility/RoomState so rooms are a HashSet of private ids, touching RPC, events, reducer, types, docs, and tests—structural product surface. A only wires an existing set_garden_pin clear into ranked child pin glyphs plus CSS/test updates, a useful but localized UX polish.