feat(search): align the map view with the mockup and open it on desktop

The map view now follows option B of the results-controls mockups:

- The list sits in a pane on the left, under the result count and sort,
  and the map fills the rest of the screen below the pinned toolbar. The
  toolbar's height is measured, so the split ends 1rem above the bottom
  of the screen however the controls wrap.
- Pins are brand-teal dots and the selected one is coral. The search
  location is an ink dot, the search radius a dashed circle with its
  distance, and the view fits that circle. Tiles are muted and the zoom
  sits under the fullscreen button.
- A school picked on the map or in the list opens a card on the map
  (View, + Compare, following the basket), and its list card is ringed
  and scrolled into view. Phones keep the bottom sheet.
- The list cards show the full name, Ofsted and school type, the
  headline figure and pupils.

The map cards now follow the list rows: no England benchmark for
special schools, PRUs and AP, and no placeholder all-zero RWM (Greenmead
showed "0% RWM -62 pts vs national"). That rule moves to a shared
listRwmValue helper.

A postcode search opens on the map for desktop browsers, chosen on the
server from the user agent so the list never paints first. The client
falls back to the list below 1024px, and follows the default through
client-side navigation from the hero until the reader picks a view.

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

nextjs-app/lib/utils.ts

@@ -898,3 +898,27 @@ export function isSpecialSchool(school: { school_type?: string | null }): boolea
   const t = (school.school_type ?? '').toLowerCase();
   return /\bspecial\b/.test(t) || /pupil referral/.test(t) || /alternative provision/.test(t);
 }
+
+/**
+ * The school's combined Reading, Writing & Maths figure, or null when there is
+ * no real one to show.
+ *
+ * A placeholder all-zero row (every subject 0, the special/suppressed
+ * signature that SchoolDetailView calls ks2Placeholder) is not a score. A
+ * genuine 0% combined, where some pupils met individual subjects but not all
+ * three, is not all-zero and stays shown.
+ */
+export function listRwmValue(school: {
+  rwm_expected_pct?: number | null;
+  reading_expected_pct?: number | null;
+  writing_expected_pct?: number | null;
+  maths_expected_pct?: number | null;
+}): number | null {
+  if (school.rwm_expected_pct == null) return null;
+  const placeholder =
+    school.rwm_expected_pct === 0 &&
+    (school.reading_expected_pct ?? 0) === 0 &&
+    (school.writing_expected_pct ?? 0) === 0 &&
+    (school.maths_expected_pct ?? 0) === 0;
+  return placeholder ? null : school.rwm_expected_pct;
+}