openai/gpt-chat-latest → A (4:1)

Side A consolidates the browser posting flow into a single `POST /ui` RPC-based dispatch, introduces `resolve_web_session` to avoid repeated auth/session extraction, removes the redundant `web_post.rs` handlers, updates forms, routes, and tests, and centralizes shared logic—an architectural simplification with broad, lasting impact. Side B contains useful but narrower fixes: passing browser attribution out-of-band via `delegate_opt`, preventing an incorrect fallback when too few sibling items exist, removing a redundant UI button, and renaming `/vote/compare` to `/vote`, but these are incremental compared with A's substantial refactor.