feat(school-detail): mobile section nav becomes a menu; Compare shrinks to an icon

Fixes the cramped mobile bar where Back, the carried Compare pill and All ▾ all
competed with the scrolling section links:

- On mobile the horizontal swipe strip collapses into a single "Section: <current> ▾"
  button that opens the existing jump-to-section sheet — no fragile horizontal
  swipe, and it doubles as a "you are here" indicator.
- The carried Compare CTA becomes a compact 38px icon on mobile (compare-arrows +
  "add" badge; flips to a teal check when in the comparison), so it no longer
  crowds the section control. Desktop keeps the labelled pill.
- Back is icon-only on mobile (label hidden), text on desktop.
- Desktop is unchanged: horizontal links + All ▾, full CTA in the hero.

Both the mobile section menu and the desktop All ▾ open the same sheet.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lh7Js5xSetKNzLVr9ArXLF

nextjs-app/components/SchoolDetailView.module.css

@@ -205,6 +205,7 @@
     flex: none;
     display: inline-flex;
     align-items: center;
+    gap: 0.3rem;
     padding: 0.3rem 0.625rem;
     font-size: 0.75rem;
     font-weight: 600;
@@ -294,6 +295,119 @@
     color: white;
 }
 
+/* ── Mobile: the scrolling links collapse into one "section" menu button ──
+   (hidden on desktop, where the links fit). */
+.sectionNavMenu {
+    display: none; /* shown only ≤640px */
+    flex: 1;
+    min-width: 0;
+    align-items: center;
+    justify-content: space-between;
+    gap: 0.5rem;
+    min-height: 38px;
+    padding: 0.34rem 0.7rem;
+    background: var(--bg-secondary, #f3ede4);
+    border: 1px solid var(--border-color, #e5dfd5);
+    border-radius: 8px;
+    cursor: pointer;
+    font-family: var(--font-dm-sans), "DM Sans", sans-serif;
+    color: var(--text-primary, #1a1612);
+}
+
+.sectionNavMenuCur {
+    display: flex;
+    align-items: center;
+    gap: 0.45rem;
+    min-width: 0;
+}
+
+.sectionNavMenuEyebrow {
+    flex: none;
+    font-size: 0.64rem;
+    font-weight: 600;
+    letter-spacing: 0.04em;
+    text-transform: uppercase;
+    color: var(--text-muted, #6d685f);
+}
+
+.sectionNavMenuNow {
+    font-size: 0.85rem;
+    font-weight: 600;
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+.sectionNavMenuChev {
+    flex: none;
+    color: var(--text-muted, #6d685f);
+    font-size: 0.7rem;
+}
+
+/* Compact icon version of the Compare CTA, used on mobile. */
+.sectionNavCompareIcon {
+    display: none; /* shown only ≤640px */
+    position: relative;
+    flex: none;
+    align-items: center;
+    justify-content: center;
+    width: 38px;
+    height: 38px;
+    border-radius: 9px;
+    border: 1px solid var(--accent-coral, #e07256);
+    background: var(--accent-coral, #e07256);
+    color: white;
+    cursor: pointer;
+    transition: background 0.15s ease, border-color 0.15s ease;
+}
+
+.sectionNavCompareIcon svg {
+    width: 19px;
+    height: 19px;
+}
+
+.sectionNavCompareBadge {
+    position: absolute;
+    top: -5px;
+    right: -5px;
+    width: 16px;
+    height: 16px;
+    border-radius: 50%;
+    background: var(--bg-card, white);
+    color: var(--accent-coral-dark, #c45a3f);
+    border: 1.5px solid var(--accent-coral, #e07256);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    font-size: 0.7rem;
+    font-weight: 800;
+    line-height: 1;
+}
+
+.sectionNavCompareIconIn {
+    background: var(--bg-card, white);
+    border-color: var(--accent-teal, #2d7d7d);
+    color: var(--accent-teal, #2d7d7d);
+}
+
+/* Swap which controls show at the mobile breakpoint. */
+@media (max-width: 640px) {
+    .sectionNavLinks,
+    .sectionNavCompare,
+    .sectionNavAll,
+    .sectionNavBackLabel {
+        display: none;
+    }
+
+    .sectionNavMenu {
+        display: flex;
+    }
+
+    .sectionNavCompareIcon {
+        display: inline-flex;
+    }
+}
+
 /* Compare CTA carried into the bar once the hero's button scrolls away. */
 .sectionNavCompare {
     flex: none;
@@ -333,13 +447,9 @@
     }
 }
 
-/* "All ▾" jump menu. */
+/* "All ▾" jump menu (desktop). */
-.sectionNavAllWrap {
-    flex: none;
-    position: relative;
-}
-
 .sectionNavAll {
+    flex: none;
     display: inline-flex;
     align-items: center;
     gap: 0.25rem;

nextjs-app/components/SchoolDetailView.tsx

@@ -291,6 +291,9 @@ export function SchoolDetailView({
 
   const heroAcademicYear = latestResults ? formatAcademicYear(latestResults.year) : '';
 
+  // Label shown in the mobile "section" menu button — the section in view.
+  const activeNavLabel = (navItems.find((n) => n.id === activeSection) ?? navItems[0])?.label ?? '';
+
   return (
     <div className={styles.container}>
       {/* Header */}
@@ -450,8 +453,12 @@ export function SchoolDetailView({
 
       {/* Sticky Section Navigation — docks under the global header */}
       <nav className={styles.sectionNav} aria-label="Page sections">
-        <button onClick={handleBack} className={styles.sectionNavBack}>← Back</button>
+        <button onClick={handleBack} className={styles.sectionNavBack} aria-label="Back">
+          <span aria-hidden="true">←</span>
+          <span className={styles.sectionNavBackLabel}>Back</span>
+        </button>
 
+        {/* Desktop: scrolling section links */}
         <div
           ref={sectionLinksRef}
           className={`${styles.sectionNavLinks}${sectionNavAtEnd ? ` ${styles.atEnd}` : ''}`}
@@ -468,18 +475,58 @@ export function SchoolDetailView({
           ))}
         </div>
 
-        {/* The hero's Compare CTA, carried in once it scrolls out of view */}
+        {/* Mobile: a single "section" menu button that opens the jump sheet */}
+        {navItems.length > 0 && (
+          <button
+            type="button"
+            className={styles.sectionNavMenu}
+            aria-haspopup="menu"
+            aria-expanded={sectionsOpen}
+            onClick={() => setSectionsOpen((o) => !o)}
+          >
+            <span className={styles.sectionNavMenuCur}>
+              <span className={styles.sectionNavMenuEyebrow}>Section</span>
+              <span className={styles.sectionNavMenuNow}>{activeNavLabel}</span>
+            </span>
+            <span className={styles.sectionNavMenuChev} aria-hidden="true">▾</span>
+          </button>
+        )}
+
+        {/* The hero's Compare CTA, carried in once it scrolls out of view.
+            Desktop shows a labelled pill; mobile a compact icon. */}
         {!heroCtaVisible && (
+          <>
             <button
               onClick={handleComparisonToggle}
               className={`${styles.sectionNavCompare}${isInComparison ? ` ${styles.sectionNavCompareIn}` : ''}`}
             >
               {isInComparison ? '✓ Comparing' : '+ Compare'}
             </button>
+            <button
+              onClick={handleComparisonToggle}
+              className={`${styles.sectionNavCompareIcon}${isInComparison ? ` ${styles.sectionNavCompareIconIn}` : ''}`}
+              aria-label={isInComparison ? 'In comparison' : 'Add to compare'}
+              title={isInComparison ? 'In comparison' : 'Add to compare'}
+            >
+              {isInComparison ? (
+                <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2.4" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
+                  <path d="m5 12 5 5 9-11" />
+                </svg>
+              ) : (
+                <>
+                  <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" aria-hidden="true">
+                    <path d="M4 7h13l-3-3" />
+                    <path d="M20 17H7l3 3" />
+                  </svg>
+                  <span className={styles.sectionNavCompareBadge} aria-hidden="true">+</span>
+                </>
+              )}
+            </button>
+          </>
         )}
 
+        {/* Desktop: "All ▾" trigger (same sheet as the mobile section menu) */}
         {navItems.length > 0 && (
-          <div className={styles.sectionNavAllWrap}>
           <button
             type="button"
             className={styles.sectionNavAll}
@@ -489,11 +536,14 @@ export function SchoolDetailView({
           >
             All <span aria-hidden="true">▾</span>
           </button>
+        )}
+
+        {/* Shared jump-to-section sheet (dropdown on desktop, bottom sheet on mobile) */}
         {sectionsOpen && (
           <>
             <div className={styles.sectionsBackdrop} onClick={() => setSectionsOpen(false)} />
             <div className={styles.sectionsPanel} role="menu" aria-label="Jump to section">
-                  <div className={styles.sectionsPanelHead}>On this page</div>
+              <div className={styles.sectionsPanelHead}>Jump to section</div>
               {navItems.map(({ id, label }) => (
                 <a
                   key={id}
@@ -512,8 +562,6 @@ export function SchoolDetailView({
             </div>
           </>
         )}
-          </div>
-        )}
       </nav>
 
       {/* Ofsted Rating / Report Card */}