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]>

CHANGELOG.md

@@ -63,12 +63,12 @@
 
 ## [Unreleased]
 
-- Street Level: Google Street View is the second provider. Light its chip
-  (off by default: every panorama is billed to the Google Maps key, which
-  needs the Maps JavaScript API) and click a street to open Google's own
-  panorama in the panel, with its arrows, the address and month in the
-  caption, a link to Google Maps and FOLLOW on Google 3D. Share links carry
-  it as `g`.
+- Street Level: Google Street View is the second provider. On the Google 3D
+  map (Google's terms keep it off other maps), light its chip (off by
+  default: every panorama is billed to the Google Maps key, which needs the
+  Maps JavaScript API) and click a street to open Google's own panorama in
+  the panel, with its arrows, the address and month in the caption, a link
+  to Google Maps and FOLLOW. Share links carry it as `g`.
 
 - Stdio servers from one install share a panel key so a page read from one
   process can make requests through another. Concurrent malformed-key repairs