~anthropic/claude-sonnet-latest → A (3:2)

A does a genuine cross-cutting refactor: it introduces `room_route_segment`/`room_id_from_route_segment` helpers to replace ad-hoc split_once logic scattered across many files, plus a new URL-normalization module (with solid test coverage) that fixes real identity bugs like YouTube URL variants and query-order collisions. B is a smaller, useful bugfix (attribution leak, dead swap button, route rename) but touches far less surface and adds less lasting infrastructure than A's DRY refactor and normalization logic.