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

Commit B delivers substantial new functionality—session-cookie web auth, a unified /post ingestion path, room-scoped thread views/routes (ThreadNav abstraction), and full router wiring—representing real, lasting feature/architecture work despite including some noise (a speculative plan2.md, Cargo.lock churn). Commit A is a small, focused set of UI polish fixes (vote-count tooltip, HUD unpin-via-POST instead of link, CSS/test tweaks) which is useful but narrow in scope and impact compared to B's structural additions.