A diff's review-comment row and its resolve control draw §5's card and button, and .dl-review, .rc-resolve* leave the markup #4706

Done:

• [ ] In src/web/diff-view.ts the inline review row draws its thread as §5's card() and the resolve control as btn(); a resolved thread is the card's muted state. No dl-review or rc-resolve class in src/web outside src/web/style/.
• [ ] A test renders a pull's Files page with an open and a resolved review comment and asserts both and the resolve button.
• [ ] The Files page timing test still passes.

Markup only: the stylesheet and docs/DESIGN.md are not touched in this pull (their rules leave in a follow-up), so it cannot conflict with the many pulls editing src/web/style/content.ts. Run bun x tsc --noEmit, bun scripts/design-lint.ts and bun test test/design-lint.test.ts before pushing; where counts fall, lower docs/design/baseline.json in the same pull.