~anthropic/claude-sonnet-latest → B (6:4)

Side B removes dead/unused complexity (ThreadVisibility, unused RoomState field, HashMap→HashSet simplification) and adds a genuinely useful CLI command (`room create`) with docs and tests updated across multiple layers (rpc.rs, events.rs, reducer.rs, timeline.rs, CLI, integration tests, bb tests). Side A is a smaller, focused UI feature (clickable pin/unpin) with decent browser test coverage but touches fewer architectural layers and has more narrowly scoped value.