fix(places): phase links must stay in their own namespace

Every place page built its phase links as /schools/[slug]/[phase], the
shape that belongs to towns alone.

On an authority page that pointed into the town namespace. For 87 of the
151 authorities the target does not exist and the link 404s; for the
other 64 it resolves to the town of the same name — a different set of
schools, which is precisely the near-duplicate the two namespaces were
introduced to prevent. On an outcode page it 404s outright.

Two causes behind it, both a rule written twice and inherited by only
one of the places that needed it.

The authority phase route was in the spec and dropped by the plan, which
built the three bare routes and no fourth. The sitemap is generated from
the place registry, which was right about them all along, so 302
authority phase URLs have been submitted to Google and every one 404s.
Adding the route makes the sitemap true and serves a real query —
admissions are authority-run, so "primary schools in Kent" is how a
parent searches before they have settled on a town.

The outcode variants were the opposite: the registry computed phases for
outcodes although the spec gives them no route, and the sitemap knew to
skip them while the API did not. The registry now decides alone, and the
sitemap's duplicate of that rule is gone.

Also: an authority under the five-school threshold has no page, so the
API sends a null slug for it and the page names it without linking.
Two English authorities are in that position. It was unreachable in
today's data — verified across the EC and TR outcodes — but the thin
place redirect would have sent a reader to a 404 the year it isn't.

The e2e journey now walks every /schools link a page of each family
emits and requires a 200, which is the check that was missing.

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

e2e/tests/journeys.spec.ts

@@ -1909,6 +1909,57 @@ test('phase variants are submitted in the places sitemap', async ({ page }) => {
   expect(xml).toMatch(/\/schools\/[a-z0-9-]+\/primary</);
 });
 
+test('authority phase variants are submitted, and in their own namespace', async ({ page }) => {
+  // 302 of these were in the sitemap for weeks and every one 404'd: the spec
+  // called for the route, the plan built the bare authority page and dropped
+  // it, and the sitemap — written from the registry — kept submitting them.
+  const xml = await (await page.request.get('/sitemaps/places-1.xml')).text();
+  expect(xml).toMatch(/\/schools\/authority\/[a-z0-9-]+\/primary</);
+});
+
+test('every place link a place page emits resolves', async ({ page }) => {
+  /*
+   * The guard that was missing. Each family built its own links, so a URL
+   * shape belonging to one namespace was used by all four: an authority page
+   * offered "Primary schools in Barnet" pointing at /schools/barnet/primary,
+   * the *town*. For 87 of 151 authorities that 404'd; for the other 64 it
+   * quietly served a different set of schools under the same name.
+   *
+   * Only /schools links are followed. The per-school links are the same
+   * component the school-page journeys already cover, and there are hundreds
+   * of them on a page.
+   */
+  for (const kind of ['town', 'authority', 'outcode'] as const) {
+    const place = await firstPlaceOfKind(page, kind);
+    const prefix = kind === 'authority' ? '/schools/authority/'
+      : kind === 'outcode' ? '/schools/near/' : '/schools/';
+    await page.goto(`${prefix}${place.slug}`);
+
+    const hrefs = [...new Set(
+      await page.locator('a[href^="/schools"]').evaluateAll(
+        (els) => els.map((e) => e.getAttribute('href')!)))];
+    expect(hrefs.length, `${kind} page links no other place`).toBeGreaterThan(0);
+
+    for (const href of hrefs) {
+      const res = await page.request.get(href);
+      expect(res.status(), `${kind} page links ${href}`).toBe(200);
+    }
+  }
+});
+
+test('an outcode page offers no phase link, because no such page exists', async ({ page }) => {
+  // Nobody searches "primary schools in SW11", so the spec gives outcodes no
+  // phase route. The registry computed the variants anyway and the page
+  // linked them, putting two 404s on each of 1,720 outcode pages.
+  const place = await firstPlaceOfKind(page, 'outcode');
+  const detail = await (await page.request.get(
+    `/api/places/outcode/${place.slug}`)).json();
+  expect(detail.place.phases).toEqual([]);
+
+  await page.goto(`/schools/near/${place.slug}`);
+  await expect(page.getByRole('navigation', { name: 'By phase' })).toHaveCount(0);
+});
+
 test('no page title repeats the brand', async ({ page }) => {
   // The root layout appends '| schoolcompare' to a plain-string title. Any
   // route whose title already carries the brand must opt out with
@@ -1947,8 +1998,15 @@ test('a place straddling a boundary names every authority it sits in', async ({
   await page.goto(`/schools/near/${straddling!.slug}`);
 
   for (const a of detail.place.authorities) {
-    await expect(page.locator(`a[href="/schools/authority/${a.slug}"]`).first())
-      .toBeVisible();
+    if (a.slug) {
+      await expect(page.locator(`a[href="/schools/authority/${a.slug}"]`).first())
+        .toBeVisible();
+    } else {
+      // No page of its own — City of London and the Isles of Scilly are
+      // under the threshold. Named, deliberately not linked.
+      await expect(page.locator('header p')).toContainText(a.name);
+      await expect(page.getByRole('link', { name: a.name })).toHaveCount(0);
+    }
   }
 });