openai/gpt-chat-latest → A (8:1)

Side A introduces a new `RouteContext` abstraction (`server/src/html/routing.rs`) and exports it from `server/src/html/mod.rs`, creating a centralized API for scoped URL generation (`item_href`, `thread_url`, room/public handling) that supports an ongoing architectural refactor. It also adds a detailed migration plan (`plan.md`) documenting the intended replacement of `CanonicalItemUrl` with `ItemId` and the phased implementation strategy, whereas Side B is overwhelmingly workspace-wide formatting plus tooling configuration (`rust-toolchain.toml`, VS Code settings) with only a minor CSS rule merge and no substantial behavioral change.