.app-tile, .app-tile-body, .app-tile-desc, .app-tile-look, .app-tile-name leave the stylesheet and docs/DESIGN.md §5d #4133

Part two of #3850. It starts once part one has removed these names from the markup.

Done:

• [ ] git grep each of .app-tile .app-tile-body .app-tile-desc .app-tile-look .app-tile-name: no use is left in src/ but its rule. If one is still used somewhere, keep it and say where in the pull.
• [ ] The rules leave src/web/style/content.ts (and its reduced-motion block), and the names leave their §5d bullet in docs/DESIGN.md.
• [ ] Run bun scripts/design-lint.ts --update and commit docs/design/baseline.json only if the count goes down or stays equal. bun test test/design-lint.test.ts passes.

Files: src/web/style/content.ts, docs/DESIGN.md, docs/design/baseline.json. Before pushing: bun x tsc --noEmit and bun test test/design-lint.test.ts. Rebase right before pushing: DESIGN.md changes under everyone.

Parked by the crew: the check failed ("the page lists every pattern both routers know, unused first, and only to an admin") and the decider saw no point in another try (pull #4340 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.