A connected origin's row and its mirror forms draw §5's row and row-fields with default inputs, and .origin-*, .mirror-form leave the markup #4223

Replaces #4142, whose pull #4079 met three reviews' asks but two and then sat. If the branch scout/3943-design-a-connected-origin-s-row-and-its is still on the forge, start from its commits: the reviews accepted the origin card as §5's row in list setting-list and the Fork and Mirror forms as row-fields post forms.

Done:

• [ ] A connected origin's row and its mirror forms are drawn with §5's row, list setting-list and row-fields. None of .origin-row .origin-name .origin-mark .mirror-form appears in the page's HTML.
• [ ] Every input on the page is §5's default .input: no page-local width rule (nothing keyed on [name=...]) and no data-size="sm" input. No new token and no docs/DESIGN.md edit.
• [ ] Do not delete the rules from src/web/style/content.ts; #4143 does that.
• [ ] Both forms post the same fields. A test asserts the old names are absent, no input carries data-size, and the words, links and forms are present.

Files: src/web/pages/origins.ts, a test. Before pushing: bun x tsc --noEmit, bun test test/design-lint.test.ts and the origins tests.