fix(street-level): IC8 review of the Street View provider

Google's Maps Platform terms forbid Street View imagery beside non-Google
maps, so the provider declares requiresMapStack: 'photoreal': off Google
3D its chip is dashed with the reason, lookups and opens skip it, and
leaving Google 3D closes its panorama.

- Ground clicks: only a click on the map itself (scenePick.isSurfacePick:
  nothing picked or Google 3D tile content) at street zoom opens Street
  View, and the camera stays put; higher up the hint says to zoom in.
  scenePick.pickGroundPosition replaces the copy in Directions.
- Viewer: poses go out at once and again when the date and address
  arrive, so an open never hangs on that lookup; one lookup per panorama,
  seeded by the nearest lookup; a close settles a pending open; failed
  lookups are asked again; poses follow position changes, not pano_changed.
- Loader: the gm_authFailure handler is installed once, so a retried load
  reports a refusal once.
- Viewer host: a prewarm that lands after another provider took the host
  is released; FIT/FILL availability is set on every open.
- Provider: a refusal while switched off reports no error over another
  photo; SINCE compares against the end of Google's month; messages name
  the referrer and network causes; FLAT says Street View is 360° only.
- The layer row names the key of the providers that are on; the MCP panel
  CSP admits Street View's tiles, control images and photos.
- Tests for each, against fakes that now follow Google's event order; the
  browser gate restores its state, waits instead of sleeping, aims its
  panel clicks and corner drags, and asserts the camera stays put.

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

src/layers/streetLevel/viewerHost.js

@@ -79,7 +79,6 @@ export function createViewerHost({ state, parts }) {
       warm.unmount();
     }
     const adapter = entry.instance.viewer;
-    state.street.renderModes = typeof adapter.setRenderMode === 'function';
     const promise = (async () => {
       await adapter.mount(state.street.host);
       if (mounting?.promise !== promise) {
@@ -139,6 +138,8 @@ export function createViewerHost({ state, parts }) {
     try {
       const adapter = await mount(entry);
       if (!current()) return false;
+      // Per open: close() resets it, and a reopen skips mount().
+      state.street.renderModes = typeof adapter.setRenderMode === 'function';
       await adapter.open(String(imageId));
       if (!current()) return false;
       if (ticket && !state.street.follow) parts.follow.lookAtPosition(ticket);
@@ -201,9 +202,11 @@ export function createViewerHost({ state, parts }) {
       } catch {
         /* the real open reports errors */
       }
-      if (active?.id === entry.def.id) continue;
-      // Switched off while it loaded: release it now rather than keep it.
-      if (!state.enabled || !entry.on) adapter.unmount();
+      if (active?.id === entry.def.id || mounting?.id === entry.def.id)
+        continue;
+      // Switched off while it loaded, or another provider's viewer took the
+      // host meanwhile: release it now rather than keep it under that one.
+      if (!state.enabled || !entry.on || active || mounting) adapter.unmount();
       else warmed.set(entry.def.id, adapter);
     }
   }