ci: speed up Frontend Typecheck + Tests; cancel superseded PR runs

The job does ~3s of real work (typecheck 1.4s + jest 1.3s) but installs
452 MB / 460 packages every run. Two changes:

- Cache nextjs-app/node_modules keyed on the lockfile hash (OS + node
  major pinned) and skip npm ci entirely on a hit — deps change rarely,
  so most PR pushes now do zero install. On miss, npm ci runs with
  --prefer-offline --no-audit --no-fund.
- Workflow-level concurrency with cancel-in-progress: a new commit (or an
  empty re-trigger) aborts the previous run instead of stacking a second
  full matrix.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

.gitea/workflows/pr-checks.yml

@@ -5,6 +5,13 @@ on:
     branches:
       - main
 
+# Cancel superseded runs: pushing a new commit to a PR (or an empty
+# re-trigger) aborts the previous still-running checks instead of running
+# a second full matrix alongside them.
+concurrency:
+  group: pr-checks-${{ gitea.event.pull_request.number }}
+  cancel-in-progress: true
+
 env:
   REGISTRY: privaterepo.sitaru.org
   BACKEND_IMAGE_NAME: ${{ gitea.repository }}-backend
@@ -23,12 +30,22 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: 22
-          cache: npm
-          cache-dependency-path: nextjs-app/package-lock.json
+
+      # Cache the resolved node_modules (452 MB / 460 packages) keyed on the
+      # lockfile. On a hit — the common case, since deps change rarely — the
+      # whole `npm ci` step is skipped, not just its download phase. The key
+      # pins OS + node major so we never restore incompatible native binaries.
+      - name: Cache node_modules
+        id: node-modules-cache
+        uses: actions/cache@v4
+        with:
+          path: nextjs-app/node_modules
+          key: nextjs-node-modules-${{ runner.os }}-node22-${{ hashFiles('nextjs-app/package-lock.json') }}
 
       - name: Install dependencies
+        if: steps.node-modules-cache.outputs.cache-hit != 'true'
         working-directory: nextjs-app
-        run: npm ci
+        run: npm ci --prefer-offline --no-audit --no-fund
 
       - name: Typecheck
         working-directory: nextjs-app

e2e/tests/journeys.spec.ts

@@ -19,27 +19,6 @@ function schoolLinks(page: Page) {
   return page.locator('a[href^="/school/"]');
 }
 
-/**
- * Two URNs guaranteed to be pure-primary (same phase). The compare page's
- * phase tabs split all-through schools (which carry KS4 data) onto the
- * secondary tab, so picking two arbitrary "primary" search hits can land
- * them on different tabs where only the active one renders. Selecting via
- * the API by exact phase keeps both on the same tab. Data-invariant: uses
- * whatever primaries the environment holds.
- */
-async function twoPrimaryUrns(page: Page): Promise<[string, string]> {
-  const res = await page.request.get('/api/schools?search=primary&per_page=50');
-  expect(res.ok()).toBeTruthy();
-  const body = await res.json();
-  const urns: string[] = (body.schools ?? [])
-    .filter((s: { phase?: string; rwm_expected_pct?: number | null }) =>
-      s.phase === 'Primary' && s.rwm_expected_pct != null,
-    )
-    .map((s: { urn: number }) => String(s.urn));
-  expect(urns.length).toBeGreaterThanOrEqual(2);
-  return [urns[0], urns[1]];
-}
-
 test('home page loads with hero search', async ({ page }) => {
   await page.goto('/');
   await expect(page.locator('h1').first()).toBeVisible();
@@ -160,13 +139,19 @@ test('results map fullscreen falls back to an overlay on iOS', async ({ page })
 });
 
 test('comparing two schools shows the parent-first sections side by side', async ({ page }) => {
-  // Two same-phase (pure primary) schools so both stay on one tab.
-  const [urn0, urn1] = await twoPrimaryUrns(page);
+  // Collect two school URNs from search results, then load the share URL
+  await searchByName(page, 'primary');
+  await expect(schoolLinks(page).first()).toBeVisible({ timeout: 15_000 });
+  const hrefs = await schoolLinks(page).evaluateAll((links) =>
+    links.map((l) => (l as HTMLAnchorElement).getAttribute('href') || '')
+  );
+  const urns = [...new Set(hrefs.map((h) => h.match(/\/school\/(\d+)/)?.[1]).filter(Boolean))];
+  expect(urns.length).toBeGreaterThanOrEqual(2);
 
-  await page.goto(`/compare?urns=${urn0},${urn1}`);
+  await page.goto(`/compare?urns=${urns[0]},${urns[1]}`);
   // Both schools' detail links should render in the comparison view
-  await expect(page.locator(`a[href*="${urn0}"]`).first()).toBeVisible({ timeout: 15_000 });
-  await expect(page.locator(`a[href*="${urn1}"]`).first()).toBeVisible();
+  await expect(page.locator(`a[href*="${urns[0]}"]`).first()).toBeVisible({ timeout: 15_000 });
+  await expect(page.locator(`a[href*="${urns[1]}"]`).first()).toBeVisible();
 
   // The parent-first sections render in order (data-invariant: headings only)
   for (const heading of [