openai/gpt-5.3-chat → B (1:4)

A simply removes a small HTML preview block (`vote-compare-preview-wrap`), reducing UI without clear functional gain. B introduces a new `routing.rs` module with `RouteContext` abstraction and wires it into `html/mod.rs`, establishing a centralized path-building design that affects future HTML and routing consistency, plus a detailed plan guiding a large refactor.