The page shell's top bar and wide mode are named in docs/design/areas/shell.md, and their classes leave §5d #5496

For: the page shell every page sits in is one component, not a set of page-local classes waiting in docs/DESIGN.md §5d. It moves to its own area file, the way the design system now grows (scripts/design-lint.ts: an area file under docs/design/areas/ is vocabulary, and parallel pulls never edit the same lines).

Done:

• [ ] A new docs/design/areas/shell.md names the component, what it is for, the function that draws it (src/web/layout.ts) and each class in a code span: .topbar-search, .topbar-tools, .hide-lg, .shell-wide. Follow docs/design/areas/README.md and the shape of the existing area files.
• [ ] Each of those classes' own lines leaves §5d in docs/DESIGN.md. Only those lines; §5d keeps one class per line, so other pulls never meet.
• [ ] No markup and no stylesheet rule changes. Every page that draws it looks the same as before.
• [ ] bun scripts/design-lint.ts passes, and so does the test that checks every defined class is documented.

Files: docs/design/areas/shell.md (new), docs/DESIGN.md (deleting lines in §5d only). Risk: none; documentation only. If design-lint asks for something else, follow what it names.