Design: the front page's featured app draws §5's card and the tiles' look, and front-featured* leave §5d #4084

Replaces #3940 (parked twice: a spent review loop, then the design check's baseline). Waits for #4063.

Done:

• [ ] The featured section in src/web/studio/home.ts is a §5 card with the look image the app tiles use, with the same link, image and words.
• [ ] .front-featured, .front-featured-look, .front-featured-body leave src/web/style/content.ts (and the reduced-motion block) and leave §5d.
• [ ] A test asserts the old names are absent and the featured link and image are present; the home tests and bun x tsc --noEmit pass.

Before you push, run bun test test/design-lint.test.ts and bun scripts/design-lint.ts: every line they print names the file and what to change; fix each one. Striking a class from docs/DESIGN.md §5d and removing its rule from the stylesheet go in the same commit, and a class you keep stays named. Rebase onto main right before pushing: docs/DESIGN.md changes under everyone.

Files: src/web/studio/home.ts, src/web/style/content.ts, docs/DESIGN.md, docs/design/baseline.json, a test.

Parked by the crew: the check failed ("a crew run's own app hosts > (unnamed)") and the decider saw no point in another try (pull #4246 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Parked by the crew: the check failed ("naming teams, at every door > one reviewer on both teams gets one run, and their approval answers both") and the decider saw no point in another try (pull #4442 closed).

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the check failed ("a crew run's own app hosts > (unnamed)") and the decider saw no point in another try (pull #4246 closed)
2. the check failed ("naming teams, at every door > one reviewer on both teams gets one run, and their approval answers both") and the decider saw no point in another try (pull #4442 closed)

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Replaced by #4596. Both tries went red on tests the change never touched (migrate-after, origins-reconnect, livetriage, snapshot-mirror, strangers, or an "(unnamed)" hook timeout); those are now planned as #4577–#4582. The fresh issue keeps the diff to the named files and says to run design-lint and lower the baseline in the same pull.