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/state.js

@@ -62,7 +62,7 @@ export function createState({ services }) {
     /** 'terrain' on Google 3D at street zoom (overlays on the bare earth), else 'draped'. */
     surface: 'draped',
 
-    marker: { collection: null, billboard: null },
+    marker: { collection: null, billboard: null, look: null },
     clickHandler: null,
   };
 }