openai/gpt-chat-latest → B (20:1)

Side B adds a substantial new Rust module that introduces core application functionality, including theme handling, static asset serving, JavaScript response/building utilities, layout rendering, linkification, media embedding, routing exports, and associated helper logic and tests. Side A only removes two Babashka tasks from `bb.edn` and renames a remaining task from `walkthrough-fixture` to `fixture`, which is a small maintenance/configuration cleanup with limited lasting impact.