fix(search): address review on the shared result rows

- The rows' narrow layout now switches at a 608px list, not 600px. Below
  769px the page pads 1rem each side, so a 640px screen gives a 608px
  list: exactly the old max-width: 640px media query, where 600px left
  633-640px screens on the wide layout.
- rowContainerGuard.test.ts fails if anything other than HomeView renders
  SchoolRow or SecondarySchoolRow, or if one of HomeView's row lists loses
  its `results` container. Outside one the rows silently keep their wide
  layout on phones. (Checked: HomeView is the only importer today.)
- Picking a pin from the list beside the map now works from the keyboard:
  each row carries a "Show <school> on the map" button, visually hidden
  until focused, with aria-pressed for the selected school. The row itself
  cannot be the button, since it holds links and buttons of its own.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

nextjs-app/__tests__/components/ResultsMapView.test.tsx

@@ -156,10 +156,19 @@ it('builds no list cards on a phone, where the pane is hidden', async () => {
 
 it('draws the list view\'s own row beside the map, with the same content', async () => {
   const { container } = await renderMap();
-  const beside = (container.querySelector('[data-urn="2"]') as HTMLElement).textContent;
+  const beside = container.querySelector('[data-urn="2"] > [class~="row"]')!.textContent;
 
   fireEvent.click(screen.getByRole('button', { name: 'List' }));
   const row = screen.getByRole('link', { name: 'Southmead Primary School' }).closest('[class~="row"]')!;
   expect(row.parentElement?.className).toMatch(/schoolList/);
   expect(row.textContent).toBe(beside);
 });
+
+it('lets a keyboard pick a pin from the list, with a real button', async () => {
+  await renderMap();
+  const show = screen.getByRole('button', { name: 'Show Southmead Primary School on the map' });
+  expect(show).toHaveAttribute('aria-pressed', 'false');
+  fireEvent.click(show);
+  expect(screen.getByTestId('map')).toHaveAttribute('data-selected', '2');
+  expect(show).toHaveAttribute('aria-pressed', 'true');
+});