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

Side B performs a substantial, coherent refactor that moves path/URL logic into a shared slug-types crate with type-safe newtypes (GardenItemUrl, ForumThreadUrl, TildeOntologyPath), reducing duplication and making the wire format correct-by-construction across server modules and RPC responses, backed by preserved/expanded tests. Side A is a smaller dev-tooling improvement (fixture persistence via cargo-watch) plus an unrelated, undocumented removal of room page headers, offering less durable architectural value than B's cross-cutting type-safety refactor.