~x-ai/grok-latest → B (2:5)

B delivers lasting end-to-end product value by adding cookie sessions, web login/logout, /r/* room pages, thread listing/pagination under private scopes, and POST /post compose forms that rewrite the forum HTML layer for multi-room use. A is valuable but narrower: it mainly adds the CLI `room create` path and simplifies the model (drop ThreadVisibility, rooms HashMap→HashSet) plus test/docs updates, which is solid prep work rather than the broader usable feature surface in B.