Design: a repository's path head and its two-column layout use the design system, and path-head/repo-layout leave §5d #3944

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:

• [ ] The path head over a tree or file and the code-plus-about layout in src/web/pages/repo.ts (.path-head, .repo-layout) are drawn from §5's crumbs and base layout utilities. The about column still sits beside the code from desktop width and below it at 390 px.
• [ ] 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/pages/repo.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.

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 #3958 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Steward (trevato): pull #3958 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 #3958 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 stayed red through 2 automatic tries (pull #4450 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 #3958 closed)
2. the check stayed red through 2 automatic tries (pull #4450 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.

Split into #4591 and #4592. 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, and splits the markup move from the rule removal.