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.js

@@ -106,18 +106,11 @@ export class StreetLevelControls {
     this.listen(el.providerChips, 'click', (event) => {
       const button = event.target?.closest?.('.data-toggle-chip');
       if (!button || button.disabled) return;
-      // A chip without a usable key stays focusable for its tooltip; a click
-      // that would light it, or switch the layer off through it, says the
-      // same thing instead. Other chips still switch (a refused Street View
-      // key cannot lock Mapillary out), and it darkens beside a lit one.
-      const providers = this._view?.providers || [];
-      const chip = providers.find(
+      // A keyless chip shows its tooltip instead of switching; others switch.
+      const chip = this._view?.providers.find(
         (entry) => entry.id === button.dataset.chipId,
       );
-      const othersLit = providers.some(
-        (entry) => entry.id !== chip?.id && entry.active,
-      );
-      if (chip?.state === 'error' && (!chip.active || !othersLit)) {
+      if (chip?.state === 'error') {
         if (button.title) this.actions.showToast?.(button.title);
         return;
       }
@@ -141,8 +134,6 @@ export class StreetLevelControls {
     this.listen(el.sinceRange, 'change', () =>
       this._setParams({ sinceDays: sinceDays() }),
     );
-    // The keyboard path to Street View: its nearest image at the view centre,
-    // without moving the camera.
     this.listen(el.nearestBtn, 'click', () => {
       const nearest = this._view?.nearest;
       if (!nearest?.visible || nearest.disabled) return;
@@ -261,24 +252,23 @@ export class StreetLevelControls {
   }
 
   /**
-   * Lighting a chip turns the layer on; darkening the last lit one turns the
-   * layer off but keeps the provider on, so the layer comes back with it.
+   * Lighting a chip turns the layer on and darkens the others (one source at
+   * a time); darkening the lit one turns the layer off, keeping the provider.
    */
   async _toggleProvider(providerId) {
     const chip = this._view?.providers.find((entry) => entry.id === providerId);
     if (!chip) return;
     if (!chip.active) {
-      this._setParams({ [providerId]: true });
+      // Every registered provider in one update (those hidden on this map
+      // too), so the share link records the swap.
+      const ids =
+        this.layer.providerIds || this._view.providers.map((entry) => entry.id);
+      this._setParams(
+        Object.fromEntries(ids.map((id) => [id, id === providerId])),
+      );
       await this._ensureEnabled();
       return;
     }
-    const othersLit = this._view.providers.some(
-      (entry) => entry.id !== providerId && entry.active,
-    );
-    if (othersLit) {
-      this._setParams({ [providerId]: false });
-      return;
-    }
     try {
       await this.actions.setEnabled?.(false);
     } catch (error) {