~x-ai/grok-latest → A (3:1)

A turns the walkthrough fixture into a lasting dev loop (cargo-watch reload, persistent fixture-data/, preferred port 8080, reuse/rebase of seeded summary) plus a small room-page cleanup—substantive ongoing DX. B only deletes a dead zero-ratio early-return and retunes one test; useful hygiene, but far less project impact than the fixture redesign.