Merge upstream/main: KartaView provider meets i18n

Upstream's KartaView PR (#1121) extracted the Mapillary coverage engine
into a shared lineCoverage.js and made the panel wording
provider-specific (coverage noun/action, SINCE upload-date note,
highlightsSequence legend gate), again in the regions this branch
localizes.

- mapillary/coverage.js: taken as upstream's thin re-export of the new
  lineCoverage.js; the generic too-high hint stays msg()-marked, now in
  lineCoverage.js where the default lives.
- kartaview/policy.js: coverage hints (tooHigh, noCoverage) marked as
  msg() data so they translate like every other coverage hint; thrown
  error messages stay English, matching the Mapillary precedent.
- presentMeta: KartaView counts streets, and Russian plurals need the
  noun inside the template, so the count line gets its own literal tn
  pair keyed off coverageLabel.noun, falling back to the sequences pair;
  upstream's noun/action data contract is untouched.
- uiState legend: upstream highlightsSequence gate with t('Selected');
  sinceNote localized with a {names} placeholder.
- layer-panels.html: sl-since-note wiring kept, data-i18n hooks kept.
- CHANGELOG: both sides kept. es/ru: 4 new keys each.

npm run i18n complete (953 messages each); npm test 6504/6506 (the one
failure is the pre-existing environmental OPENAI_API_KEY leak in
devFreshDotenv, unrelated); build passes.

src/app/layers/streetLevel.js

@@ -1,6 +1,7 @@
 import { createStreetLevelLayer } from '../../layers/streetLevel/index.js';
 import { createMapillaryProvider } from '../../layers/streetLevel/providers/mapillary/index.js';
 import { createGoogleProvider } from '../../layers/streetLevel/providers/google/index.js';
+import { createKartaViewProvider } from '../../layers/streetLevel/providers/kartaview/index.js';
 import * as sprites from '../../data/spriteOrder.js';
 import * as picking from '../../data/pickRegistry.js';
 import * as input from '../../data/inputOwnership.js';
@@ -10,12 +11,16 @@ import * as render from '../../renderGovernor.js';
 /** The browser Maps key the scene was started with (src/app/scene.js). */
 const googleApiKey = () => globalThis.window?.__GOOGLE_MAPS_API_KEY__ || null;
 
-/** Mapillary and Google Street View, once the Mapillary source is supplied; else none. */
+/**
+ * Mapillary, Google Street View and KartaView, once the Mapillary source is
+ * supplied; else none.
+ */
 function defaultProviders(sources) {
   if (sources.mapillary == null) return [];
   return [
     createMapillaryProvider({ source: sources.mapillary }),
     createGoogleProvider({ getApiKey: googleApiKey }),
+    createKartaViewProvider(),
   ];
 }
 

src/app/layers/streetLevel.test.mjs

@@ -28,7 +28,7 @@ test('explicit providers replace the default source and an empty list removes it
   );
 });
 
-test('the defaults are Mapillary (given its source) and Street View, which starts off and travels as a provider switch', async () => {
+test('the defaults are Mapillary (given its source), Street View and KartaView, which start off and travel as provider switches', async () => {
   const { createDefaultLayerState } = await import('../../data/layerState.js');
   const mapillary = {
     getStatus() {},
@@ -37,7 +37,7 @@ test('the defaults are Mapillary (given its source) and Street View, which start
     nearestImages() {},
   };
   const layer = createApplicationStreetLevel({ sources: { mapillary } });
-  assert.deepEqual(layer.providerIds, ['mapillary', 'google']);
+  assert.deepEqual(layer.providerIds, ['mapillary', 'google', 'kartaview']);
   // A fresh page and a restored default agree: Street View is billed, so off.
   layer.setParams(createDefaultLayerState().options['street-level']);
   assert.equal(layer.getParams().google, false);
@@ -45,7 +45,12 @@ test('the defaults are Mapillary (given its source) and Street View, which start
   // A link that lit Street View carries it in the shared switch field.
   layer.setParams({ providerSwitches: 'google-1' });
   assert.equal(layer.getParams().google, true);
-  assert.equal(layer.getParams().providerSwitches, 'google-1');
+  assert.equal(layer.getParams().providerSwitches, 'google-1*kartaview-0');
+  // KartaView is keyless and free, but one source shows at a time.
+  layer.setParams({ providerSwitches: 'kartaview-1' });
+  assert.equal(layer.getParams().kartaview, true);
+  assert.equal(layer.getParams().google, false);
+  assert.equal(layer.getParams().mapillary, false);
   // Without the application's Street Level source there are none.
   assert.deepEqual(createApplicationStreetLevel({}).providerIds, []);
 });