fix(school): show Nursery only for nursery classes, and say Girls' school

GIAS NurseryProvision is text ("Has Nursery Classes", "No Nursery
Classes", "Not applicable"), but the header and the place table tested it
for truthiness. Every school with a value got a Nursery chip or a "Yes",
including secondaries aged 11-18. hasNurseryClasses() matches the one
value that means a nursery, and the type now says the field is a string.

The single-sex chip appended 's to the plural GIAS gender, giving
"Girls's school". singleSexLabel() gives "Girls' school" / "Boys' school".

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

e2e/tests/journeys.spec.ts

@@ -3286,3 +3286,23 @@ for (const width of [360, 390, 430]) {
     expect(failing).toEqual([]);
   });
 }
+
+/*
+ * The header's facts row read GIAS text as booleans: "Not applicable" put a
+ * "Nursery" chip on secondaries aged 11–18, and "Girls" became "Girls's
+ * school". Data-invariant: the chip follows whatever the API says.
+ */
+test('a girls\' secondary header names it properly and shows Nursery only when it has one', async ({ page }) => {
+  const res = await page.request.get('/api/schools?search=school&phase=secondary&gender=girls&per_page=1');
+  expect(res.ok()).toBeTruthy();
+  const [school] = (await res.json()).schools ?? [];
+  test.skip(!school, 'no girls\' secondary in this environment');
+  const detail = await (await page.request.get(`/api/schools/${school.urn}`)).json();
+
+  await page.goto(`/school/${school.urn}`);
+  const header = page.locator('header', { has: page.getByRole('heading', { level: 1 }) });
+  await expect(header.getByText("Girls' school", { exact: true })).toBeVisible({ timeout: 15_000 });
+  await expect(header.getByText(/'s school/)).toHaveCount(0);
+  await expect(header.getByText('Nursery', { exact: true }))
+    .toHaveCount(detail.school_info.nursery_provision === 'Has Nursery Classes' ? 1 : 0);
+});