feat(seo): add school name to URLs, fix sticky nav, collapse compare widget

- URLs now /school/138267-school-name instead of /school/138267
- Bare URN URLs redirect to canonical slug (backward compat)
- Remove overflow-x:hidden that broke sticky tab nav on secondary pages
- ComparisonToast starts collapsed — user must click to open

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextjs-app/components/RankingsView.tsx

@@ -8,7 +8,7 @@
 import { useRouter, usePathname, useSearchParams } from 'next/navigation';
 import { useComparison } from '@/hooks/useComparison';
 import type { RankingEntry, Filters, MetricDefinition } from '@/lib/types';
-import { formatPercentage, formatProgress } from '@/lib/utils';
+import { formatPercentage, formatProgress, schoolUrl } from '@/lib/utils';
 import { EmptyState } from './EmptyState';
 import styles from './RankingsView.module.css';
 
@@ -267,7 +267,7 @@ export function RankingsView({
                         )}
                       </td>
                       <td className={styles.schoolCell}>
-                        <a href={`/school/${ranking.urn}`} className={styles.schoolLink}>
+                        <a href={{schoolUrl(ranking.urn, ranking.school_name)}} className={styles.schoolLink}>
                           {ranking.school_name}
                         </a>
                       </td>
@@ -277,7 +277,7 @@ export function RankingsView({
                         <strong>{displayValue}</strong>
                       </td>
                       <td className={styles.actionCell}>
-                        <a href={`/school/${ranking.urn}`} className="btn btn-tertiary btn-sm">View</a>
+                        <a href={{schoolUrl(ranking.urn, ranking.school_name)}} className="btn btn-tertiary btn-sm">View</a>
                         <button
                           onClick={() => handleAddToCompare(ranking)}
                           disabled={alreadyInComparison}