fix(admissions): move the cut-off detail into its own section

The admissions card measured 1503px on a live school page — half the height
of every section put together, and nearly three times the next largest — with
its default view rendering as four tiles adrift in about 1080px of blank card.

The cause was a layout trick meeting content it was never sized for. The
admissions views are stacked in one grid cell so switching them never shifts
layout, and the hidden ones keep their box: only visibility is dropped. That
works while the views are comparable. The distance view added in #102 carries
a chart, a table and a map, came to 1402px against the tile grid's 316px, and
pinned every other view to its height — including the one that renders by
default, which nobody had clicked.

Rather than only unpinning it, the detail moves out. Every other topic on the
page is a section with a nav entry, and "how close did we need to live, and
would we have got in?" is a topic, not a variant reading of the intake
figures. The headline number stays on the Admissions tile where the intake
story is; the record behind it now lives in a Distance section directly below.

  admissions   1503px -> 554px
  distance        new -> 743px   (median section on the page is ~528px)

Three further changes, each of which also makes the content better rather
than only shorter:

  * The map renders on request. Before a postcode is entered it is a circle
    drawn round a school, and it costs a Leaflet bundle and 240px to say so;
    a successful check opens it automatically, which is the point at which it
    starts answering something. Map height 320px -> 240px.
  * The chart appears only at the four published years that let the summary
    state a direction. Below that we already refuse to call the series a
    trend, and a line through three points asserts one regardless of what the
    sentence beneath it admits. The table carries those years anyway, with
    the reasons a line cannot show.
  * Three caveat paragraphs become one. They said walking-route twice and
    made the same point about priorities in two voices. It now sits in
    CutoffDistanceDetail rather than inside the check, so it still renders
    for a school with coordinates missing, where there is a table but no map
    and no check.

The new e2e guard asserts no section exceeds 2.5x the median section height.
Measuring the card's internals cannot catch this: the tile grid is flex: 1,
so it absorbs the stretch and every box still looks full. The first version
of this test targeted an arbitrary primary, passed against the live bug, and
proved nothing; pointed at a school that actually holds cut-off history it
fails on staging with "#admissions is 1459px against a 526px median".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WDvkyqqHABm4bmth2kjAxE

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

@@ -132,13 +132,30 @@ describe('CutoffMapPanel', () => {
     expect(screen.getByRole('alert')).toHaveTextContent(/Something went wrong/);
   });
 
-  it('always states the limits of the check', async () => {
+  it('does not carry the caveat itself', () => {
+    // It moved to CutoffDistanceDetail so it renders once per section, and so
+    // it still appears for a school with no coordinates (no map, no check).
+    // Asserting its absence here is what stops the old three-paragraph stutter
+    // creeping back.
     renderPanel([d(2024, 800)]);
-    // Present before any postcode is entered, not revealed with the answer.
-    expect(screen.getByText(/An indication only/)).toBeInTheDocument();
-    // The two caveats divide the work: the map says the rings are not a
-    // boundary, the check says the measurement may not be a straight line.
-    expect(screen.getByText(/not a catchment boundary/)).toBeInTheDocument();
-    expect(screen.getByText(/walking route rather than a straight line/)).toBeInTheDocument();
+    expect(screen.queryByText(/Distance is the last criterion/)).not.toBeInTheDocument();
+  });
+
+  it('keeps the map behind a request until there is a reason to show it', async () => {
+    renderPanel([d(2024, 800)]);
+    expect(screen.queryByTestId('cutoff-map')).not.toBeInTheDocument();
+
+    // A successful check is that reason: the rings only answer a question once
+    // there is a home to sit beside them.
+    mockGeocode.mockResolvedValue(northOf(200));
+    await check('SE23 3NA');
+    await screen.findByRole('status');
+    expect(screen.getByTestId('cutoff-map')).toBeInTheDocument();
+  });
+
+  it('can also show the map without a postcode, on request', () => {
+    renderPanel([d(2024, 800)]);
+    fireEvent.click(screen.getByRole('button', { name: /Show these distances on a map/ }));
+    expect(screen.getByTestId('cutoff-map')).toBeInTheDocument();
   });
 });