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/registry.js

@@ -10,11 +10,12 @@
  * @property {{coverage: string}} colors   The source's one colour, from policy.js PROVIDER_COLORS.
  * @property {{html: string}} credit   On-globe attribution while the provider is active.
  * @property {boolean} [groundClick]   No coverage to click: a click on the ground at street zoom opens its nearest image.
+ * @property {string} [requiresMapStack]   Usable only on this map stack (Google Street View: 'photoreal', per Google's terms).
  * @property {boolean} [defaultOn]     Switched on until the user says otherwise (default true); match the share-link option default.
  * @property {(context: ProviderContext) => ProviderInstance} create
  *
  * @typedef {object} ProviderContext   Handed to `create()` once by the core.
- * @property {object} services         Scene services: picking, input, render, sprites, ground, terrain.
+ * @property {object} services         Scene services: picking, input, render, sprites, ground, terrain, scenePick (ground clicks need it).
  * @property {() => {pano: string, sinceMs: number|null}} getFilter   Filter resolved against now; read it on every use so "since N days" keeps up.
  * @property {() => boolean} isActive  Layer enabled and this provider switched on.
  * @property {() => 'draped'|'terrain'} getSurface   'terrain' on Google 3D at street zoom: draw on bare earth.