~x-ai/grok-latest → A (2:1)

A adds lasting product/design substance: room URLs become a single validated `/r/{short}{slug}` segment via `room_route`, plus real external identity work (`url_normalize`, YouTube rewrites, query sorting, dash path case rules) wired through canonicalize and call sites/tests. B is valuable but mainly a move of existing canonicalization/path helpers into `slug-types` with GardenItemUrl/ForumThreadUrl newtypes and re-exports—structural centralization and API typing more than new behavior.