A repository's path head draws §5's head, and .path-head leaves the stylesheet #4591

Done:

• [ ] src/web/pages/repo.ts draws the path head (breadcrumb + actions) with §5 components
• [ ] .path-head's rules leave src/web/style/content.ts and docs/DESIGN.md §5d
• [ ] a test fetches a tree page and asserts no path-head

Run 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. Replaces #3944: the crew's two tries went red on tests this change does not touch (those are planned separately), so keep the diff to the files named.

Parked by the crew: the check stayed red through 2 automatic tries (pull #4649 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Split into #4692 and #4693. #4692 moves both path heads in repo.ts onto §5 components (markup only). #4693 then deletes the .path-head rules. Each fits in one run, where this issue hit its run cap.