fix: center named places on their own location

A place's bounds can reach far from the place itself; Tokyo's include
remote Pacific islands, so the middle of its box is open ocean. Keep the
geocoder's point for a named place and use it as the area's center,
while bounds still decide what lies inside the area.

src/tools/area.test.mjs

@@ -1,6 +1,6 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
-import { areaContains, distanceKm, resolveArea } from './area.js';
+import { areaCenter, areaContains, distanceKm, resolveArea } from './area.js';
 import { placeFromGeocodeResult } from './places.js';
 
 test('an area needs exactly one form', async () => {
@@ -91,6 +91,7 @@ test('geocode results become bounded places', () => {
     {
       name: 'Oslo, Norway',
       bounds: { west: 10.5, south: 59.8, east: 10.9, north: 60 },
+      point: { lat: 59.9, lon: 10.7 },
     },
   );
   assert.deepEqual(
@@ -100,3 +101,19 @@ test('geocode results become bounded places', () => {
   );
   assert.equal(placeFromGeocodeResult({ geometry: {} }), null);
 });
+
+test('a named place centers on its own point, not the middle of its bounds', async () => {
+  // Tokyo's prefecture bounds reach remote Pacific islands.
+  const places = {
+    resolve: async () => ({
+      name: 'Tokyo, Japan',
+      bounds: { west: 136.07, south: 20.21, east: 153.99, north: 35.9 },
+      point: { lat: 35.6769, lon: 139.7639 },
+    }),
+  };
+  const tokyo = await resolveArea({ place: 'Tokyo' }, { services: { places } });
+  assert.deepEqual(areaCenter(tokyo), { lat: 35.6769, lon: 139.7639 });
+  assert.equal(areaContains(tokyo, { lat: 27.09, lon: 142.19 }), true);
+  const box = await resolveArea({ bbox: [0, 0, 10, 10] });
+  assert.deepEqual(areaCenter(box), { lat: 5, lon: 5 });
+});