openai/gpt-chat-latest → A (8:1)

Side A introduces a new `RouteContext` abstraction (`server/src/html/routing.rs`) and re-exports it, creating a centralized API for building scoped HTML routes (`item_href`, `thread_url`, room/public handling) that supports future refactoring away from ad hoc URL construction. Although much of the patch is planning documentation, the code change establishes a reusable architectural boundary, whereas Side B mainly alters the forum compose UI (removing the toggle, labels, and changing placeholders/button text) without adding comparable long-term infrastructure.