fix(street-level): camera height over Google 3D, cast only when it helps, gate token

From the code review of #768:

- view.js measured the camera's height above ground with globe.getHeight,
  but Google 3D hides the globe, so coverage picked its zoom from the
  ellipsoidal height. Over a high city (Denver, ~1,600 m) a camera 500 m up
  read 2,100 m: coverage stayed at z12/z13, whose tiles are too big to cast,
  and lines stayed draped on the roofs. With the globe hidden, the bare-earth
  height from the ground caster now answers; coverage re-picks its zoom when
  the surface mode changes. Verified in Denver: terrain mode, z14, cast lines.
  The core's surface check uses the same helper (and no longer subtracts the
  2 m lift from the camera height).
- castTile rebuilt a tile even when no line could be cast (terrain proxy
  down, tile too big); it now leaves such tiles as they are.
- The feature gate read Street Level's share token as a literal `0`; it now
  takes it from LAYER_STATE_REGISTRY, since a rebase can reassign it.

New view.test.mjs covers the shown-globe, hidden-globe and no-sample cases.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

scripts/format-scope.json

@@ -901,6 +901,7 @@
   "src/layers/streetLevel/pickRouter.test.mjs",
   "src/layers/streetLevel/uiState.test.mjs",
   "src/layers/streetLevel/groundCast.test.mjs",
+  "src/layers/streetLevel/view.test.mjs",
   "src/layers/streetLevel/providers/mapillary/provider.test.mjs",
   "src/layers/streetLevel/providers/mapillary/decode.test.mjs",
   "src/ui/panelDock.test.mjs",