fix: say when the camera catalog serves only part of a region

Camera packs keep their nearest cameras and the catalog cap thins them
further, so London answered 250 cameras while TfL offers many more. The
catalog now records each pack's full count, tags cameras with their pack,
and serves the packs it trimmed; find_cctv_cameras names them.

src/data/cctvCatalogCap.test.mjs

@@ -128,6 +128,10 @@ test('the catalog applies the fair cap to configured packs end to end', async ()
       sources.slice(0, 3).map((s) => s.id),
       ['env-0', 'env-1', 'env-2'],
     );
+    assert.equal(sources[0].pack, 'env');
+    assert.deepEqual(getSources.trimmedPacks(), [
+      { pack: 'env', available: 12, served: 9 },
+    ]);
   } finally {
     for (const key of Object.keys(process.env)) {
       if (!(key in saved)) delete process.env[key];
@@ -135,3 +139,19 @@ test('the catalog applies the fair cap to configured packs end to end', async ()
     Object.assign(process.env, saved);
   }
 });
+
+test('a pack trimmed to its nearest cameras reports how many it offered', async () => {
+  const { prioritizeSources } =
+    await import('../../server/providers/cctv/normalize.js');
+  const cameras = Array.from({ length: 5 }, (_, i) => ({
+    id: `c${i}`,
+    lat: i,
+    lon: 0,
+  }));
+  const kept = prioritizeSources(cameras, 2, [{ lat: 0, lon: 0 }]);
+  assert.deepEqual(
+    kept.map((camera) => camera.id),
+    ['c0', 'c1'],
+  );
+  assert.equal(kept.available, 5);
+});