~anthropic/claude-sonnet-latest → B (8:2)

Side B is a substantial, coherent refactor that extracts forum.rs into focused submodules (nav, ingest, room_members, new_thread, access) plus a useful new sampling script/task, improving maintainability without changing behavior. Side A is a small, valid bugfix/clarification (turning silent fallback into an explicit expect and fixing docs/tests for 0-based thread_post_index), which is correct but much narrower in lasting impact.