Design: the front page's admin controls use §5's row, bar and field, and front-admin/pick/pin-any/weights leave §5d #3941

For: the design audit (#2678). One page part at a time onto §5's components (src/web/ui.ts helpers such as row, card, badge, btn, field, empty, and §5 classes), so docs/DESIGN.md §5d only shrinks.

Done:

• [ ] frontControls in src/web/studio/home.ts (.front-admin, .front-pick, .front-pin-any, .front-weights) is drawn from §5's row, .bar, field and btn, and posts the same fields to /front.
• [ ] Those classes' rules are gone from src/web/style/content.ts (and from the reduced-motion block, if listed there), and their names leave the style/content.ts bullet of docs/DESIGN.md §5d. bun scripts/design-lint.ts passes, and --update gives a lower or equal baseline.
• [ ] Nothing a person reads or taps is lost, and every form posts the same fields. A test asserts the old class names are absent from the page's HTML, the page's existing tests pass, and bun x tsc --noEmit passes before the push. Screenshots are not required; the sandbox has no browser.

Files: src/web/studio/home.ts, src/web/style/content.ts, docs/DESIGN.md, the test. Risk: another page borrowing a class. git grep each name first, and if one is used elsewhere, keep it and say so in the pull. #3850 and #3870 also edit home.ts: rebase onto whichever lands first.

Parked by the crew: the check failed in the place it ran, not in the change, and failed the same way when it was run again (pull #3955 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Steward (trevato): pull #3955 was parked by an infrastructure fault, not this work - the egress cap from #3719 stopped every check's package install (02:20-03:12Z). The forge is rolled back and the cap is fixed (c7ea1935). Reopened and re-checked; this strike does not count.

Parked by the crew: the check failed ("design check: nothing added outside the system (#2678) > the tree is no worse than its baseline") and the decider saw no point in another try (pull #3955 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 ("design check: nothing added outside the system (#2678) > the tree is no worse than its baseline") and the decider saw no point in another try (pull #4077 closed).

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

1. the check failed ("design check: nothing added outside the system (#2678) > the tree is no worse than its baseline") and the decider saw no point in another try (pull #3955 closed)
2. the check failed ("design check: nothing added outside the system (#2678) > the tree is no worse than its baseline") and the decider saw no point in another try (pull #4077 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 #4085, which waits for #4063 (both parks were the design check's baseline test) and for #4084 so two pulls do not edit home.ts at once.