feat(search): fall back to keyless Photon geocoding

Place search was Google-only: searchAndFlyTo threw without a key, and with a
key whose Geocoding API is not enabled it returned nothing. Both cases leave
the LOCATION box and the fly_to_location voice tool unable to resolve a name,
even though every other layer in the app works keyless.

src/keylessGeocoder.js adapts Photon (komoot, over OpenStreetMap) into the
shape the Google path already produces — lat/lng, label, Google-style types,
{southwest,northeast} bounds — so geocodeNavigationMode, regionFramingPlan and
the region-swath cap keep running on unchanged inputs. The translation lives at
the boundary and nowhere else; Google remains primary and its branch is
unchanged when it answers.

Detection is the empty result, not an exception: an unenabled Geocoding API
answers HTTP 200 with REQUEST_DENIED. Places near-view recovery is now
attempted only when a key exists, since Places is a Google service too.

Three translations are load-bearing, and each was found by querying the live
service rather than by reasoning about OSM tagging:

- Google's `bounds` PREFERS results inside the box; Photon's `bbox` FILTERS to
  it. Sent as a bbox, searching "Ho Guom, Ha Noi" while looking at Austin
  returns features: []. Sent as Photon's lat/lon proximity bias it finds the
  lake, and "Sixth Street" still resolves to Austin's over Austin and to
  England's over London.
- Photon's `extent` is [west, north, east, south]. Read as [w,s,e,n] it yields
  an inverted but finite box that frames the camera at nothing.
- A specific OSM key=value rule must beat the coarse `type`. Photon tags a lake
  `water=lake` with `type: 'other'` — unmapped, that framed Hoan Kiem Lake as a
  precise place and put the camera 26 m over the water — and tags a town square
  `type: 'locality'`, which framed Times Square as if it were a city.

searchAndFlyTo no longer throws when no key is present. Both callers already
read a null return as not-found (ui.js renders its miss branch, gevActions
reports ok: false), so the removed throw has no consumer.

Verified end to end through the real search box, with a key Google refuses:
one denied Google geocode, one Photon request, camera from Austin
(30.2700, -97.7400) to 21.0288, 105.8524 — Hoan Kiem Lake to within metres —
and "Ha Noi" framed at province scale. npm test 2604/2604; npm run build
clean; npm run test:track 97/3, the same three failures unmodified main
produces on this machine.

src/keylessGeocoder.test.mjs

@@ -0,0 +1,199 @@
+// KEYLESS GEOCODER — the Photon adapter that keeps place search working
+// without a Google key.
+//
+// The whole value of this module is that its output is INDISTINGUISHABLE to
+// everything downstream: `geocodeNavigationMode` and the framing code must keep
+// making the same decisions they make on a Google result. So these tests check
+// the translation, not the network — three things that go wrong silently:
+//
+//   1. Photon's `extent` is [west, north, east, south]. Read as [w,s,e,n] it
+//      yields an inverted-but-plausible box, and the camera frames nonsense.
+//   2. Photon calls a national park `type: 'other'`. Dropped, a park geocodes
+//      as a precise place and the camera lands on a random patch of grass —
+//      the exact bug geocodeNavigationMode's area types exist to prevent.
+//   3. A miss must be `null`, never a throw: both callers read null as
+//      "not found" and a throw would surface as a broken search box.
+//
+// Run with: npm test
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  geocodeKeyless,
+  normalizePhotonFeature,
+  photonExtentToBounds,
+  photonResultLabel,
+  photonResultTypes,
+  photonSearchUrl,
+} from './keylessGeocoder.js';
+import { geocodeNavigationMode } from './locations.js';
+
+/** Photon's real answer for "Hanoi", trimmed to the fields we consume. */
+const HANOI = {
+  geometry: { type: 'Point', coordinates: [105.854041, 21.0283334] },
+  properties: {
+    osm_key: 'place',
+    osm_value: 'city',
+    type: 'city',
+    name: 'Hà Nội',
+    country: 'Việt Nam',
+    countrycode: 'VN',
+    extent: [105.2889615, 21.3854176, 106.0200407, 20.5645154],
+  },
+};
+
+test('a city normalizes into the shape the Google path produces', () => {
+  const result = normalizePhotonFeature(HANOI);
+
+  assert.equal(result.lat, 21.0283334);
+  assert.equal(result.lng, 105.854041);
+  assert.equal(result.label, 'Hà Nội, Việt Nam');
+  assert.deepEqual(result.types, ['locality']);
+  assert.equal(geocodeNavigationMode(result.types), 'city-overview');
+});
+
+test('the extent is read as [west, north, east, south], not as [w,s,e,n]', () => {
+  const bounds = photonExtentToBounds(HANOI.properties.extent);
+
+  // Hanoi spans roughly 20.56..21.39 N and 105.29..106.02 E. A [w,s,e,n] read
+  // would put north at 21.385 and south at 106.02 — a box that still has four
+  // finite numbers and would frame the camera at nothing.
+  assert.equal(bounds.southwest.lat, 20.5645154);
+  assert.equal(bounds.northeast.lat, 21.3854176);
+  assert.equal(bounds.southwest.lng, 105.2889615);
+  assert.equal(bounds.northeast.lng, 106.0200407);
+  assert.ok(bounds.northeast.lat > bounds.southwest.lat, 'north must exceed south');
+  assert.ok(bounds.northeast.lng > bounds.southwest.lng, 'east must exceed west');
+});
+
+test('a malformed or out-of-range extent yields no bounds rather than a bad box', () => {
+  assert.equal(photonExtentToBounds(undefined), null);
+  assert.equal(photonExtentToBounds([1, 2, 3]), null);
+  assert.equal(photonExtentToBounds([0, 95, 10, -95]), null, 'latitude past the pole');
+  assert.equal(photonExtentToBounds([-200, 10, 10, 0]), null, 'longitude past the antimeridian');
+});
+
+test('area features keep an area type so the camera frames them, not a rooftop', () => {
+  // Every row is a real Photon answer, captured from the live service. The
+  // lake rows are why: Photon tags water as `water=lake`, not `natural=water`,
+  // and the guess cost a camera 26 m over Hoan Kiem Lake.
+  const cases = [
+    [{ type: 'other', osm_key: 'water', osm_value: 'lake' }, 'natural_feature', 'area-overview'],
+    [{ type: 'other', osm_key: 'leisure', osm_value: 'park' }, 'park', 'area-overview'],
+    [{ type: 'other', osm_key: 'place', osm_value: 'region' }, 'natural_feature', 'area-overview'],
+    [{ type: 'other', osm_key: 'natural', osm_value: 'peak' }, 'natural_feature', 'area-overview'],
+    [{ type: 'other', osm_key: 'waterway', osm_value: 'river' }, 'natural_feature', 'area-overview'],
+    [{ type: 'house', osm_key: 'aeroway', osm_value: 'aerodrome' }, 'airport', 'area-overview'],
+    [{ type: 'house', osm_key: 'amenity', osm_value: 'university' }, 'university', 'area-overview'],
+    [{ type: 'street', osm_key: 'highway', osm_value: 'motorway' }, 'route', 'street-corridor'],
+    [{ type: 'country', osm_key: 'place', osm_value: 'country' }, 'country', 'region-overview'],
+    [{ type: 'state', osm_key: 'place', osm_value: 'state' }, 'administrative_area_level_1', 'region-overview'],
+    [{ type: 'district', osm_key: 'place', osm_value: 'suburb' }, 'sublocality', 'neighborhood-close'],
+  ];
+
+  for (const [properties, expectedType, expectedMode] of cases) {
+    const types = photonResultTypes(properties);
+    assert.ok(
+      types.includes(expectedType),
+      `${properties.osm_key}=${properties.osm_value} must carry ${expectedType}, got ${JSON.stringify(types)}`,
+    );
+    assert.equal(geocodeNavigationMode(types), expectedMode);
+  }
+});
+
+test('a tag rule wins over the coarse class — a town square is not a city', () => {
+  // Photon reports Times Square and Quang truong Ba Dinh as place=square with
+  // type: 'locality'. Falling through to the coarse class framed a plaza as if
+  // it were a whole city.
+  const square = { type: 'locality', osm_key: 'place', osm_value: 'square' };
+  assert.deepEqual(photonResultTypes(square), []);
+  assert.equal(geocodeNavigationMode(photonResultTypes(square)), 'precise-place');
+});
+
+test('an ordinary building stays a precise place', () => {
+  const types = photonResultTypes({ type: 'house', osm_key: 'building', osm_value: 'yes' });
+  assert.equal(geocodeNavigationMode(types), 'precise-place');
+});
+
+test('the label names the place, then only containers it does not already name', () => {
+  assert.equal(
+    photonResultLabel({ name: 'Hoàn Kiếm Lake', district: 'Hoàn Kiếm', city: 'Hà Nội', country: 'Việt Nam' }),
+    'Hoàn Kiếm Lake, Hoàn Kiếm, Hà Nội, Việt Nam',
+  );
+  assert.equal(
+    photonResultLabel({ name: 'Hà Nội', city: 'Hà Nội', country: 'Việt Nam' }),
+    'Hà Nội, Việt Nam',
+    'a city must not repeat its own name',
+  );
+});
+
+test('the Google bias becomes a SOFT proximity bias, never a hard bbox', () => {
+  const url = new URL(photonSearchUrl('Sixth Street', { bias: '30.2000,-97.8000|30.3000,-97.7000' }));
+
+  assert.equal(url.searchParams.get('q'), 'Sixth Street');
+  assert.equal(url.searchParams.get('limit'), '1');
+  assert.equal(url.searchParams.get('lat'), '30.25', 'centre of the biased rectangle');
+  assert.equal(url.searchParams.get('lon'), '-97.75');
+
+  // Measured against the live service: Photon's bbox FILTERS, Google's bounds
+  // PREFERS. Sending the rectangle as a bbox makes every off-screen search
+  // return features: [] — "Ho Guom, Ha Noi" while looking at Austin finds
+  // nothing at all. This assertion is the guard against that regression.
+  assert.equal(url.searchParams.get('bbox'), null, 'a bbox would filter out every off-screen place');
+});
+
+test('an absent or unparsable bias drops the bias instead of sending a broken one', () => {
+  for (const bias of [undefined, 'nonsense', 'a,b|c,d']) {
+    const url = new URL(photonSearchUrl('Hanoi', bias === undefined ? {} : { bias }));
+    assert.equal(url.searchParams.get('lat'), null);
+    assert.equal(url.searchParams.get('lon'), null);
+    assert.equal(url.searchParams.get('bbox'), null);
+  }
+});
+
+test('a network failure resolves to null — callers read null as not-found', async () => {
+  const rejecting = () => Promise.reject(new Error('offline'));
+  assert.equal(await geocodeKeyless('Hanoi', { fetchImpl: rejecting }), null);
+
+  const notOk = () => Promise.resolve({ ok: false, json: () => Promise.resolve({}) });
+  assert.equal(await geocodeKeyless('somewhere else', { fetchImpl: notOk }), null);
+
+  const empty = () => Promise.resolve({ ok: true, json: () => Promise.resolve({ features: [] }) });
+  assert.equal(await geocodeKeyless('third distinct query', { fetchImpl: empty }), null);
+});
+
+test('an empty query never reaches the network', async () => {
+  let calls = 0;
+  const counting = () => { calls += 1; return Promise.reject(new Error('should not run')); };
+
+  assert.equal(await geocodeKeyless('   ', { fetchImpl: counting }), null);
+  assert.equal(await geocodeKeyless(null, { fetchImpl: counting }), null);
+  assert.equal(calls, 0);
+});
+
+test('repeat queries are served from the memo, misses included', async () => {
+  let calls = 0;
+  const counting = () => {
+    calls += 1;
+    return Promise.resolve({ ok: true, json: () => Promise.resolve({ features: [HANOI] }) });
+  };
+
+  const first = await geocodeKeyless('Ha Noi memo probe', { fetchImpl: counting });
+  const second = await geocodeKeyless('Ha Noi memo probe', { fetchImpl: counting });
+  assert.equal(calls, 1, 'the second lookup must not hit the network');
+  assert.deepEqual(second, first);
+
+  const missing = () => {
+    calls += 1;
+    return Promise.resolve({ ok: true, json: () => Promise.resolve({ features: [] }) });
+  };
+  await geocodeKeyless('typo memo probe', { fetchImpl: missing });
+  await geocodeKeyless('typo memo probe', { fetchImpl: missing });
+  assert.equal(calls, 2, 'a miss must be memoized too, or a typo costs one request per keystroke');
+});
+
+test('a feature without usable coordinates is rejected', () => {
+  assert.equal(normalizePhotonFeature(undefined), null);
+  assert.equal(normalizePhotonFeature({ properties: { name: 'Nowhere' } }), null);
+  assert.equal(normalizePhotonFeature({ geometry: { coordinates: [200, 10] } }), null);
+  assert.equal(normalizePhotonFeature({ geometry: { coordinates: [10, 91] } }), null);
+});