Form layout is named in docs/design/areas/forms.md, and .field-row and .form-actions leave §5d #5524

For: a form's row of fields and its row of actions 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/forms.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: .field-row, .form-actions. Follow docs/design/areas/README.md.
• [ ] 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/forms.md, docs/DESIGN.md (deleting lines in §5d only). Risk: none; documentation only. If a class turns out to have no rule or no markup any more, say so in the pull and leave its line for a separate retirement issue.