feat(street-level): one imagery source at a time; IC8 review fixes

- One provider is lit at a time: lighting a chip darkens the others, and a
  chip click records every registered provider's switch in one update so
  the share link keeps the swap (also off Google 3D, where Street View is
  not listed). The layer starts with the first default-on provider
  (Mapillary, free); params that light several keep the one already on,
  so reapplying them never flips (litByParams). The now-unreachable
  "several lit" chip paths are gone.
- Leaving Google 3D during a Street View lookup ends it without an error
  or a stuck loading state (openImage's early return resets it; the
  lookup loop rechecks availability).
- A source swap during a lookup no longer reports "no imagery".
- Street View lit off Google 3D says the panel needs the Google 3D map.
- Comments trimmed to the why; keySetupCore.test.mjs back to upstream's
  formatting plus the one new test (was a 551-line reformat).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/ui/streetLevelControls.test.mjs

@@ -1176,7 +1176,7 @@ test('OPEN STREET VIEW opens the nearest panorama at the view centre without mov
     assert.equal(button.hidden, true);
   }));
 
-test('a refused key on one provider leaves the other chip switchable, and the refused chip darkens beside it', () =>
+test('a refused Street View key cannot lock Mapillary out; its chip only explains itself', () =>
   withDom(async (dom) => {
     const state = uiState({ on: false, keyRequired: true });
     state.providers.push({
@@ -1194,23 +1194,37 @@ test('a refused key on one provider leaves the other chip switchable, and the re
     const chips = () => dom.root.querySelector('#sl-provider-chips').children;
     chips()[0].click(); // Mapillary: configured, dark
     await settle();
+    // One source at a time: lighting Mapillary darkens Street View too.
     assert.deepEqual(calls.setParams, [
-      [{ mapillary: true }, { origin: 'user' }],
+      [{ mapillary: true, google: false }, { origin: 'user' }],
     ]);
-    // With Mapillary lit, the refused Street View chip can be darkened.
+    // Now dark, the refused chip says why instead of lighting.
     state.providers[0].on = true;
+    state.providers[1].on = false;
     state.keyRequired = false;
     layer.publish({ ...state });
     chips()[1].click();
     await settle();
-    assert.deepEqual(calls.setParams.at(-1), [
-      { google: false },
-      { origin: 'user' },
+    assert.equal(calls.setParams.length, 1);
+    assert.deepEqual(calls.toasts, [
+      dom.root.querySelector('#sl-provider-chips').children[1].title,
     ]);
-    assert.equal(calls.toasts.length, 0);
   }));
 
-test('Street View alone hides the imagery filters and the legend; Mapillary beside it brings them back', () =>
+test('a swap names every registered provider, also those hidden on this map', () =>
+  withDom(async (dom) => {
+    const state = uiState({ on: false });
+    const { calls, layer, chip } = stubPanel(dom, state);
+    // Off Google 3D the Street View chip is not listed, but stays registered.
+    layer.providerIds = ['mapillary', 'google'];
+    chip().click();
+    await settle();
+    assert.deepEqual(calls.setParams, [
+      [{ mapillary: true, google: false }, { origin: 'user' }],
+    ]);
+  }));
+
+test('Street View lit hides the imagery filters and the legend; Mapillary lit shows them', () =>
   withDom(async (dom) => {
     const state = uiState();
     const { layer } = stubPanel(dom, state);