feat(compare): fill the sticky bar's label rail with a comparison caption

'COMPARING / 3 primary schools' — 0.72rem uppercase eyebrow over a
0.95rem semibold count, sized to sit alongside the 0.92rem chip names
without dominating. Desktop only; mobile pills unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

nextjs-app/components/ComparisonView.tsx

@@ -350,6 +350,14 @@ export function ComparisonView({
             style={{ '--school-count': activeSchools.length } as CSSProperties}
             aria-label="Schools in this comparison"
           >
+            {/* Fills the 200px label rail on desktop (hidden on mobile). */}
+            <div className={styles.barCaption}>
+              <span className={styles.barCaptionEyebrow}>Comparing</span>
+              <span className={styles.barCaptionCount}>
+                {activeSchools.length} {comparePhase} school
+                {activeSchools.length === 1 ? '' : 's'}
+              </span>
+            </div>
             {activeSchools.map((school, index) => (
               <div
                 key={school.urn}