Fix the follow-up review findings in import, layers, startup and engines

- KML/KMZ import: a per-file canvas budget and cache for ground overlays,
  limits on rings and vertices of raised polygons, overlays across 360° and
  near the poles, degenerate holes, polar and single-latitude fills,
  absolute overlays at their altitude, overlay order by drawOrder as on
  Cesium, and pins on tiles keep their measured height.
- Points on the surface: OSM Places and Street Level cones share the
  surface sampler and sit on the terrain before they are measured, within
  a sampling budget per pass; Cockpit's contact-dot bank keeps the dot
  atlas, and a failed fleet model loads again after a pause.
- Startup: the loading screen lifts after the share-link view is restored,
  the retry screen names the failed engine and takes focus, and the
  fallback toast stays for 6 s.
- Engines: an engine switch lands a running camera flight at its
  destination (camera.completeFlight on both engines), the sighting card
  leaves focus on the engine picker after a switch, and a Cesium model
  error stays with the instance that failed.
- The MCP panel builds again: its wind-mesh alias resolves to the stub.
- QA: the wildlife switch waits for the camera to rest, GBFS --w2 says it
  needs the dev server, and test fixtures are shared instead of copied.

docs/GLOBE-PRIMITIVES.md

@@ -38,7 +38,9 @@ Instances move every frame without a rebuild. `depthTest` decides whether
 the scene hides them. A pick returns the instance's `pickId` when the set is
 `pickable`. `ready(index?)` says whether a model's glTF or a sprite atlas has
 loaded and `failed(index?)` whether it failed to: a failed set is not loaded
-again, so a layer that retries makes a new set.
+again, so a layer that retries makes a new set. Cesium loads a model per
+instance: an index written with another `pickId` loads its own model, so an
+instance moved into a failed index does not inherit the failure.
 
 ## Lines: polylines in the air