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>

nextjs-app/__tests__/components/schoolDetailHeader.test.tsx

@@ -0,0 +1,66 @@
+/**
+ * The facts row under the school name.
+ *
+ * nursery_provision is GIAS text, not a boolean: "Has Nursery Classes",
+ * "No Nursery Classes" or "Not applicable". Tested for truthiness, every one
+ * of those read as a nursery, so secondaries aged 11–18 showed "Nursery".
+ */
+
+import { screen } from '@testing-library/react';
+import { primaryFixture, secondaryFixture } from '../support/schoolFixtures';
+import { renderSchoolDetail, renderSecondarySchoolDetail } from '../support/renderSchoolDetail';
+
+jest.mock('@/lib/analytics', () => ({
+  track: jest.fn(),
+  getNavigationSource: () => 'direct',
+}));
+jest.mock('@/components/PerformanceChart', () => ({
+  PerformanceChart: () => <div data-testid="performance-chart" />,
+}));
+jest.mock('@/components/SatsChart', () => ({
+  __esModule: true,
+  default: () => <div data-testid="sats-chart" />,
+}));
+jest.mock('@/components/AdmissionsTrendChart', () => ({
+  __esModule: true,
+  default: () => <div data-testid="admissions-trend-chart" />,
+}));
+jest.mock('@/components/SchoolHeroMap', () => ({
+  SchoolHeroMap: () => <div data-testid="hero-map" />,
+  __esModule: true,
+}));
+
+function withSchool<T extends { schoolInfo: object }>(fixture: T, info: object): T {
+  return { ...fixture, schoolInfo: { ...fixture.schoolInfo, ...info } };
+}
+
+describe('school header nursery chip', () => {
+  it('shows Nursery when GIAS says the school has nursery classes', () => {
+    renderSchoolDetail(withSchool(primaryFixture, { nursery_provision: 'Has Nursery Classes' }));
+    expect(screen.getByText('Nursery', { selector: 'span' })).toBeInTheDocument();
+  });
+
+  it.each(['No Nursery Classes', 'Not applicable', null])(
+    'hides Nursery when GIAS says %p',
+    (value) => {
+      renderSecondarySchoolDetail(withSchool(secondaryFixture, { nursery_provision: value }));
+      expect(screen.queryByText('Nursery', { selector: 'span' })).not.toBeInTheDocument();
+    },
+  );
+});
+
+describe('school header single-sex chip', () => {
+  it.each([['Girls', "Girls' school"], ['Boys', "Boys' school"]])(
+    'labels a %s school with a plural possessive',
+    (gender, label) => {
+      renderSecondarySchoolDetail(withSchool(secondaryFixture, { gender }));
+      expect(screen.getByText(label)).toBeInTheDocument();
+      expect(screen.queryByText(/'s school/)).not.toBeInTheDocument();
+    },
+  );
+
+  it('says nothing for a mixed school', () => {
+    renderSecondarySchoolDetail(withSchool(secondaryFixture, { gender: 'Mixed' }));
+    expect(screen.queryByText(/school$/, { selector: 'span' })).not.toBeInTheDocument();
+  });
+});