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/data/scenePick.js

@@ -47,3 +47,53 @@ export function isPickedWorldPosition(position) {
   const magnitude = Math.hypot(x, y, z);
   return magnitude >= MIN_PICK_MAGNITUDE_M && magnitude <= MAX_PICK_MAGNITUDE_M;
 }
+
+/**
+ * The world position under a screen point: the rendered surface (terrain,
+ * Google 3D) where the depth buffer has it, else the ellipsoid. Null over the
+ * sky or for a pick that names no place.
+ *
+ * @param {object} viewer A Cesium viewer.
+ * @param {{x: number, y: number}} screenPosition
+ * @returns {{x: number, y: number, z: number}|null} A Cartesian3.
+ */
+export function pickGroundPosition(viewer, screenPosition) {
+  const scene = viewer?.scene;
+  let position = null;
+  if (
+    scene?.pickPositionSupported &&
+    typeof scene.pickPosition === 'function'
+  ) {
+    try {
+      position = scene.pickPosition(screenPosition);
+    } catch {
+      position = null;
+    }
+  }
+  if (
+    !isPickedWorldPosition(position) &&
+    typeof viewer?.camera?.pickEllipsoid === 'function'
+  ) {
+    try {
+      position = viewer.camera.pickEllipsoid(screenPosition);
+    } catch {
+      position = null;
+    }
+  }
+  return isPickedWorldPosition(position) ? position : null;
+}
+
+/**
+ * Whether a `scene.pick()` result is the map itself: nothing, or Google 3D
+ * tile content, which picks without an id.
+ *
+ * @param {object|null|undefined} picked
+ * @returns {boolean}
+ */
+export function isSurfacePick(picked) {
+  if (!picked) return true;
+  if (picked.id !== undefined) return false;
+  return (
+    picked.content !== undefined || picked.primitive?.isCesium3DTileset === true
+  );
+}