A connected origin's row and its mirror forms draw §5's row, .bar, field and btn, and .origin-row, .origin-name, .origin-mark, .mirror-form leave the markup #4142

Part one of #3943, which stalled or went red as one change. This part changes only the markup; the stylesheet and docs/DESIGN.md are part two.

Done:

• [ ] A connected origin's row and its mirror forms are drawn with §5's row, .bar, field and btn from src/web/ui.ts and §5's classes. None of .origin-row .origin-name .origin-mark .mirror-form appears in the page's HTML.
• [ ] Do not delete the rules from src/web/style/content.ts 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, 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/pages/origins.ts, a test. Both forms post the same fields. Before pushing, run bun x tsc --noEmit, bun test test/design-lint.test.ts and the page's tests. No screenshots: the sandbox has no browser.

From the reviews of pull #4079 (the same page, closed): the origin card as §5's row in list setting-list and the Fork/Mirror forms as row-fields post forms were right. Two things to avoid: no page-local width rule such as [name="name"] (leave inputs at §5's default width), and no data-size="sm" input, which is 28 px on a touch screen (leave inputs at their default size). Branch scout/3943-design-a-connected-origin-s-row-and-its holds that pull's commits.

Replaced by #4223: the same markup change, with the two asks pull #4079's reviews left (default inputs, no page-local width rule) written into what done looks like.