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/SecondarySchoolRow.tsx

@@ -11,7 +11,7 @@
 'use client';
 
 import type { School } from '@/lib/types';
-
+import { schoolUrl } from '@/lib/utils';
 import styles from './SecondarySchoolRow.module.css';
 
 const OFSTED_LABELS: Record<number, string> = {
@@ -73,7 +73,7 @@ export function SecondarySchoolRow({
 
         {/* Line 1: School name + Ofsted badge */}
         <div className={styles.line1}>
-          <a href={`/school/${school.urn}`} className={styles.schoolName}>
+          <a href={{schoolUrl(school.urn, school.school_name)}} className={styles.schoolName}>
             {school.school_name}
           </a>
           {school.ofsted_grade && (
@@ -155,7 +155,7 @@ export function SecondarySchoolRow({
 
       {/* Right: actions */}
       <div className={styles.rowActions}>
-        <a href={`/school/${school.urn}`} className="btn btn-tertiary btn-sm">
+        <a href={{schoolUrl(school.urn, school.school_name)}} className="btn btn-tertiary btn-sm">
           View
         </a>
         {(onAddToCompare || onRemoveFromCompare) && (