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/SecondarySchoolDetailView.module.css

@@ -2,7 +2,6 @@
 
 .container {
   width: 100%;
-  overflow-x: hidden;
 }
 
 /* ── Header ──────────────────────────────────────────── */