The appearance picker's swatches are named in docs/design/areas/theme.md, and .swatch, .tick and .preview leave §5d #5539

For: the appearance picker's colour swatches, the tick on the chosen one, and its preview is one documented component, not page-local classes waiting in docs/DESIGN.md §5d. Area files under docs/design/areas/ are vocabulary to scripts/design-lint.ts, and parallel pulls never edit the same lines (#4063).

Done:

• [ ] docs/design/areas/theme.md (new) names the component and what it is for. For each class, in a code span, it gives the function or page that writes it (find it with grep -rn 'class="[^"]*\b<name>\b' src/web) and the stylesheet that styles it: .swatch, .tick, .preview. Follow docs/design/areas/README.md. .theme-option and .theme-apply are #4701's to retire; leave them.
• [ ] Each of those classes' own lines leaves §5d in docs/DESIGN.md. Delete only those lines.
• [ ] No markup and no stylesheet rule changes; every page looks the same.
• [ ] bun scripts/design-lint.ts passes, and so does the test that checks every defined class is documented.

Files: docs/design/areas/theme.md, docs/DESIGN.md (deleting lines in §5d only). Risk: none; documentation only. A class found with no rule or no markup is named in the pull and left for a retirement issue.