A change's, a file browse page's and the commits list's heads draw §5's page head and meta row, and .issue-head, .issue-meta leave their markup #4266

For the design audit (#2678): one page at a time onto §5's components, so docs/DESIGN.md §5d only shrinks. Part one of two: this part changes only the markup; the stylesheet and docs/DESIGN.md are part two.

Done:

• [ ] The head and meta line of a change page, a browse page and the commits list are drawn with the §5 component that fits (row, badge, bar, card, btn or field from src/web/ui.ts and §5's classes; name which in the pull). None of .issue-head, .issue-meta appears in the page's HTML.
• [ ] Do not delete the rules from the stylesheet and do not edit docs/DESIGN.md. Part two does that, and the design check stays green because the classes are still defined and named.
• [ ] Nothing a person reads or taps is lost, long unbroken text still wraps (.break), and every form posts the same fields. A test asserts the old names are absent and the words, links and forms are present.

Files: src/web/studio/change.ts, src/web/pages/browse.ts, src/web/pages/commits.ts, a test. Before pushing, run bun x tsc --noEmit, bun test test/design-lint.test.ts, bun scripts/design-lint.ts and the page's tests. No screenshots: the sandbox has no browser.