Place every surface-bound layer through the shared placement

Import pins, infrastructure, ALPR, directions markers, bikeshare and the
Bhote Koshi story use createSurfacePoints instead of their own sampling,
budgets and partial triggers; ground snap, the mesh floor sampler,
traffic, transit, Street Level, the camera ground guard, wildlife and the
cockpit host read heights through readSurface or surfaceTriggers.
Per-layer offsets and floor policies stay as options. The import no
longer re-places pins on every camera move from the UI.

Calls to engine.surface outside src/globe go from 41 sampling calls to
10, each a raycast, a one-shot fly-to height or an asynchronous detailed
sample.

scripts/engine-coupling-baseline.json

@@ -2,7 +2,7 @@
   "metrics": {
     "attachRendererWithViewer": 33,
     "restoreFlagCopies": 9,
-    "surfaceCallsOutsideGlobe": 41,
+    "surfaceCallsOutsideGlobe": 10,
     "engineSwitchLayerIds": 3,
     "cesiumLayerRendererLines": 0,
     "navaraLayerRendererLines": 0,