.origin-row, .origin-name, .origin-mark and .mirror-form leave the stylesheet #4599

No markup under src/ draws .origin-row, .origin-name, .origin-mark, .mirror-form any more; only the rules remain.

Done:

• [ ] no rule for .origin-row, .origin-name, .origin-mark, .mirror-form remains in src/web/style/content.ts
• [ ] .origin-row, .origin-name, .origin-mark, .mirror-form is gone from docs/DESIGN.md §5d
• [ ] grep -rn for each name under src/ and test/ finds nothing (a test that asserts the old name is updated to assert its absence)
• [ ] the pages that once drew them render unchanged

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 #4143: 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 #4652 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.