fix: judge camera catalog trimming by region, not by returned cameras

Coverage was checked only for packs among the cameras found, so an area
whose cameras were all trimmed away answered zero cameras, complete. The
catalog now reports where each trimmed pack's cameras are, and the tool
marks an answer partial whenever its area overlaps that region.

src/data/cctvCatalogCap.test.mjs

@@ -129,9 +129,13 @@ test('the catalog applies the fair cap to configured packs end to end', async ()
       ['env-0', 'env-1', 'env-2'],
     );
     assert.equal(sources[0].pack, 'env');
-    assert.deepEqual(getSources.trimmedPacks(), [
-      { pack: 'env', available: 12, served: 9 },
-    ]);
+    const [trimmed] = getSources.trimmedPacks();
+    assert.deepEqual(
+      { ...trimmed, region: undefined },
+      { pack: 'env', available: 12, served: 9, region: undefined },
+    );
+    assert.equal(trimmed.region.south, 30);
+    assert.ok(Math.abs(trimmed.region.north - 30.11) < 1e-9);
   } finally {
     for (const key of Object.keys(process.env)) {
       if (!(key in saved)) delete process.env[key];
@@ -154,4 +158,5 @@ test('a pack trimmed to its nearest cameras reports how many it offered', async
     ['c0', 'c1'],
   );
   assert.equal(kept.available, 5);
+  assert.deepEqual(kept.region, { west: 0, south: 0, east: 0, north: 4 });
 });