test: pin school detail behaviour before refactor

14 characterization tests covering Ofsted (both OEIF and Report Card layouts),
KS2 results with the England delta, KS4 Attainment 8 / Progress 8 / EBacc,
all-through dual rendering, special-school comparison suppression (PR #70),
the admissions year/trend toggle, and conditional section rendering.

All rendering goes through renderSchoolDetail(), the single seam the
server/client split is allowed to change. The assertions must survive the
refactor unmodified.

Excludes __tests__/support from testMatch: it holds fixtures and helpers, not
suites, and the glob was failing them as empty test files.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nextjs-app/jest.config.js

@@ -16,6 +16,9 @@ const customJestConfig = {
     '**/__tests__/**/*.[jt]s?(x)',
     '**/?(*.)+(spec|test).[jt]s?(x)',
   ],
+  // __tests__/support holds fixtures and render helpers, not test suites; the
+  // testMatch glob above would otherwise treat them as empty suites and fail.
+  testPathIgnorePatterns: ['<rootDir>/node_modules/', '<rootDir>/__tests__/support/'],
   collectCoverageFrom: [
     'app/**/*.{js,jsx,ts,tsx}',
     'components/**/*.{js,jsx,ts,tsx}',