fix(school): address review on the header chip fixes

- E2E: list with page_size (per_page was ignored), fail clearly if the
  gender filter is ignored, and require nursery_provision on the detail
  payload so the Nursery assertion cannot pass vacuously.
- singleSexLabel ignores case, as hasNurseryClasses does.
- Header test: type withSchool with Partial<School>, and match the
  single-sex labels exactly instead of any span ending in "school".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

nextjs-app/lib/utils.ts

@@ -113,8 +113,9 @@ export function hasNurseryClasses(value: string | null | undefined): boolean {
  * GIAS genders are plural, so the possessive is a bare apostrophe.
  */
 export function singleSexLabel(gender: string | null | undefined): string | null {
-  const g = gender?.trim();
-  if (g === 'Girls' || g === 'Boys') return `${g}' school`;
+  const g = gender?.trim().toLowerCase();
+  if (g === 'girls') return "Girls' school";
+  if (g === 'boys') return "Boys' school";
   return null;
 }