feat(home): compact value-prop line on the mobile hero (P1.7)

Phones showed only the poetic h1 and a bare search box — no coverage,
scope, or freshness statement above the fold for the 63%-of-entries,
56%-mobile audience. One compact line ('24,000+ English schools — SATs,
GCSEs, Ofsted & admissions, side by side. Updated for 2026/27') now
replaces the hidden eyebrow + full paragraph at ≤640px, costing ~2 short
lines. Desktop copy unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nextjs-app/components/HomeView.module.css

@@ -62,6 +62,11 @@
   font-weight: 700;
 }
 
+/* Copy variants: full paragraph ≥641px, compact merged line on phones. */
+.heroDescriptionCompact {
+  display: none;
+}
+
 @media (max-width: 768px) {
   .heroSection {
     padding-top: 1.5rem;
@@ -74,18 +79,29 @@
   }
 }
 
-/* Above the fold on phones, every line costs. Drop the eyebrow tag and the
-   long descriptive paragraph — the h1 already names the product, and the
-   search input is the primary action users came to perform. */
+/* Above the fold on phones, every line costs. Drop the eyebrow tag and swap
+   the long descriptive paragraph for one compact line that carries coverage
+   ("24,000+ schools") and freshness ("updated for 2026/27") — a first-time
+   visitor otherwise sees only a poetic h1 and a bare box, with no reason to
+   trust the data (audit P1.7, feeds the 46% home exit rate). */
 @media (max-width: 640px) {
   .heroSection {
     padding-top: 0.75rem;
     margin-bottom: 1rem;
   }
   .heroEyebrow,
-  .heroDescription {
+  .heroDescriptionFull {
     display: none;
   }
+  .heroDescriptionCompact {
+    display: block;
+  }
+  .heroDescription {
+    font-size: 0.85rem;
+    line-height: 1.4;
+    max-width: 320px;
+    margin-bottom: 0.25rem;
+  }
   .heroTitle {
     font-size: 1.65rem;
   }