feat(school-detail): move Back to a standalone link, dock "Back to top" in the nav

Replicate the Autotrader pattern: pull the page-back control out of the
sticky section-nav bar and place a standalone "← Back" text link above the
header card, on the page background, where it scrolls away with the page.
It keeps the context-aware behaviour (router.back → /search fallback); the
secondary view gains the same fallback for parity (it previously used a bare
router.back() that dead-ends on deep links).

The pinned slot the Back button vacated now holds a "↑ Top" control that
smooth-scrolls to the top, so the sticky bar keeps a useful affordance.
Applies to both primary and secondary detail views.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

nextjs-app/components/SchoolDetailView.module.css

@@ -4,6 +4,29 @@
     max-width: 100%;
 }
 
+/* Standalone back link, sits above the header card on the page background. */
+.topBack {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.4rem;
+    margin: 0 0 0.75rem;
+    padding: 0.25rem 0;
+    font-size: 1.0625rem;
+    font-weight: 600;
+    color: var(--accent-coral, #e07256);
+    background: none;
+    border: none;
+    cursor: pointer;
+    line-height: 1.2;
+    transition: color 0.15s ease;
+}
+
+.topBack:hover {
+    color: var(--accent-coral-dark, #c85a3e);
+    text-decoration: underline;
+    text-underline-offset: 2px;
+}
+
 /* Header Section */
 .header {
     background: var(--bg-card, white);

nextjs-app/components/SchoolDetailView.tsx

@@ -106,6 +106,10 @@ export function SchoolDetailView({
     }
   };
 
+  const scrollToTop = () => {
+    if (typeof window !== 'undefined') window.scrollTo({ top: 0, behavior: 'smooth' });
+  };
+
   useEffect(() => {
     const el = sectionLinksRef.current;
     if (!el) return;
@@ -306,6 +310,13 @@ export function SchoolDetailView({
 
   return (
     <div className={styles.container}>
+      {/* Standalone back link, above the header — returns to wherever the
+          user came from. Scrolls away with the page (the sticky bar keeps a
+          "back to top" control in its place). */}
+      <button type="button" onClick={handleBack} className={styles.topBack}>
+        <span aria-hidden="true">←</span> Back
+      </button>
+
       {/* Header */}
       <header className={styles.header}>
         <div className={styles.headerContent}>
@@ -439,9 +450,9 @@ 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} aria-label="Back">
-          <span aria-hidden="true">←</span>
-          <span className={styles.sectionNavBackLabel}>Back</span>
+        <button onClick={scrollToTop} className={styles.sectionNavBack} aria-label="Back to top">
+          <span aria-hidden="true">↑</span>
+          <span className={styles.sectionNavBackLabel}>Top</span>
         </button>
 
         {/* Desktop: scrolling section links */}

nextjs-app/components/SecondarySchoolDetailView.module.css

@@ -4,6 +4,29 @@
     width: 100%;
 }
 
+/* Standalone back link, sits above the header card on the page background. */
+.topBack {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.4rem;
+    margin: 0 0 0.75rem;
+    padding: 0.25rem 0;
+    font-size: 1.0625rem;
+    font-weight: 600;
+    color: var(--accent-coral, #e07256);
+    background: none;
+    border: none;
+    cursor: pointer;
+    line-height: 1.2;
+    transition: color 0.15s ease;
+}
+
+.topBack:hover {
+    color: var(--accent-coral-dark, #c85a3e);
+    text-decoration: underline;
+    text-underline-offset: 2px;
+}
+
 /* ── Header ──────────────────────────────────────────── */
 .header {
     background: var(--bg-card, white);

nextjs-app/components/SecondarySchoolDetailView.tsx

@@ -124,6 +124,20 @@ export function SecondarySchoolDetailView({
     }
   };
 
+  // Back returns wherever the user came from; deep-links fall back to search
+  // so the button never dead-ends or leaves the site.
+  const handleBack = () => {
+    if (typeof window !== 'undefined' && window.history.length > 1) {
+      router.back();
+    } else {
+      router.push('/search');
+    }
+  };
+
+  const scrollToTop = () => {
+    if (typeof window !== 'undefined') window.scrollTo({ top: 0, behavior: 'smooth' });
+  };
+
   useEffect(() => {
     track('school_viewed', {
       urn: schoolInfo.urn,
@@ -200,6 +214,12 @@ export function SecondarySchoolDetailView({
 
   return (
     <div className={styles.container}>
+      {/* Standalone back link, above the header — returns wherever the user
+          came from. Scrolls away; the sticky bar keeps a "back to top" control. */}
+      <button type="button" onClick={handleBack} className={styles.topBack}>
+        <span aria-hidden="true">←</span> Back
+      </button>
+
       {/* ── Header ─────────────────────────────────────── */}
       <header className={styles.header}>
         <div className={styles.headerContent}>
@@ -324,7 +344,7 @@ export function SecondarySchoolDetailView({
       {/* ── Sticky section navigation ─────────────────────── */}
       <nav className={styles.tabNav} aria-label="Page sections">
         <div className={styles.tabNavInner}>
-          <button onClick={() => router.back()} className={styles.backBtn}>← Back</button>
+          <button onClick={scrollToTop} className={styles.backBtn} aria-label="Back to top">↑ Top</button>
           {navItems.length > 0 && <div className={styles.tabNavDivider} />}
           {navItems.map(({ id, label }) => (
             <a