feat(street-level): Street View polish — name, filters, legend, marker

- The chip reads GOOGLE STREET VIEW (and its caption link likewise).
- Providers declare the imagery filters they honour (`filters`, default
  pano + since). Street View declares none: every panorama is 360° and it
  draws no coverage to thin, so its lookups ignore the filters and the
  panel hides IMAGERY and SINCE while it is the only lit provider.
- The legend lists only providers that draw coverage lines, with
  Selected only beside one: Street View alone shows no legend.
- Providers may pick their on-globe marker (`marker`); Street View's is a
  Google-blue field-of-view cone from a white-ringed dot, in place of
  GEV's amber pin, and switches back for a Mapillary photo.

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

src/layers/streetLevel/viewerHost.js

@@ -40,7 +40,11 @@ export function createViewerHost({ state, parts }) {
       creator: pose.creator || null,
       externalUrl: pose.externalUrl || null,
     });
-    parts.marker.set(state.street.position, state.street.bearing);
+    parts.marker.set(
+      state.street.position,
+      state.street.bearing,
+      providerEntry(pose.providerId)?.def.marker,
+    );
     parts.follow.followCamera();
     // Select the sequence only once the image is on screen, so its lookup
     // never competes with the image download.