~anthropic/claude-sonnet-latest → B (8:2)

Side B introduces a substantial, reusable architecture (a generic form-template/hole-filling system plus a unified `/ui` HTML action endpoint) that refactors duplicated POST handlers into shared functions and adds meaningful new tests, delivering lasting design value. Side A is a smaller, focused refactor (Deque→List/Vec with query-time capping) that fixes a real inefficiency but has much narrower scope and impact than B's endpoint/template infrastructure.