feat(analytics): measure the location layer, and stop calling it direct

The location pages were only half-tracked. Umami counts a pageview for
each of the ~3,900 URLs automatically, but nothing else: components/
places contained no track() call, and place_viewed was not even a
declared event name.

The part that mattered was worse than a gap. getNavigationSource mapped
a same-origin referrer to a funnel source and had no case for /schools/,
so every school view arriving through the location layer fell through to
'direct' — the bucket you read as "typed the URL, no referrer". W2's
whole purpose is funnelling search traffic onto school pages, so the one
measurement that says whether it worked was reporting the wrong answer,
and reporting it confidently. Verified live against staging: expected
"place", received "direct".

/schools/ is checked before /school/. They differ by one letter and mean
different things — the location layer versus a single school — and a
prefix test in the wrong order silently merges them.

place_viewed carries kind, slug, phase and school_count. kind is the
reason it exists: whether to keep investing in these pages turns on
which sort earns engagement, and a pageview cannot say, because all four
families share the /schools/ prefix and only the registry knows which is
which. It is a client component because PlaceView is a server component;
one line in PlaceView covers all four families, since they all render
through it.

Both E2E journeys were verified failing against staging first — one
because place_viewed does not exist there, the other on the exact
"place" vs "direct" mismatch.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015mWQnpye9F299NVRCCSRvj

nextjs-app/__tests__/lib/analytics.test.ts

@@ -0,0 +1,64 @@
+import { getNavigationSource } from '@/lib/analytics';
+
+/** jsdom's document.referrer is read-only; redefining it is the way in. */
+function referrer(url: string) {
+  Object.defineProperty(document, 'referrer', { value: url, configurable: true });
+}
+
+const ORIGIN = 'http://localhost';
+
+describe('getNavigationSource', () => {
+  afterEach(() => referrer(''));
+
+  it('attributes a visit from a location page to the place layer', () => {
+    /*
+     * The one this was added for.
+     *
+     * W2 published ~3,900 location pages whose entire purpose is to funnel
+     * search traffic onto school pages. Before this case existed they fell
+     * through to 'direct' — so the location layer's contribution was not
+     * merely missing from the funnel, it was being counted in the bucket you
+     * read as "typed the URL". The measurement that decides whether W2 worked
+     * was confidently reporting the wrong answer.
+     */
+    referrer(`${ORIGIN}/schools/barnet`);
+    expect(getNavigationSource()).toBe('place');
+  });
+
+  it.each([
+    ['/schools/authority/kent', 'authority'],
+    ['/schools/near/sw11', 'outcode'],
+    ['/schools/brentwood/primary', 'phase variant'],
+  ])('covers %s (%s)', (path) => {
+    referrer(`${ORIGIN}${path}`);
+    expect(getNavigationSource()).toBe('place');
+  });
+
+  it('still calls a school page "detail", one character away', () => {
+    // /school/ and /schools/ differ by one letter and mean different things.
+    // A prefix test written in the wrong order silently merges them.
+    referrer(`${ORIGIN}/school/100010-brecknock-primary-school`);
+    expect(getNavigationSource()).toBe('detail');
+  });
+
+  it.each([
+    ['/', 'search'],
+    ['/rankings', 'rankings'],
+    ['/compare?urns=1,2', 'compare'],
+  ])('leaves %s attributed as %s', (path, expected) => {
+    referrer(`${ORIGIN}${path}`);
+    expect(getNavigationSource()).toBe(expected);
+  });
+
+  it('treats an external referrer as direct', () => {
+    // Umami records the real referrer on the pageview; this field is only
+    // about internal navigation.
+    referrer('https://www.google.com/search?q=schools+in+barnet');
+    expect(getNavigationSource()).toBe('direct');
+  });
+
+  it('treats no referrer as direct', () => {
+    referrer('');
+    expect(getNavigationSource()).toBe('direct');
+  });
+});