Upgrade Ground Zero vegetation assets

Docs/Terrain/GroundZeroNaturalEnvironmentPass.md

@@ -9,8 +9,11 @@ space.
 - Terrain receives a procedural coastal scrub terrain material that blends
   dry soil, scrub green, and sandy path color families with broad and fine
   noise so Ground Zero does not read as flat tan placeholder ground.
-- Foliage patch instances keep the current prototype meshes but use distinct
-  tree, shrub, and dry grass materials.
+- Foliage patch instances use native low-poly coastal scrub vegetation meshes
+  under `/Game/Agrarian/Environment/Vegetation`: a coastal oak proxy, coyote
+  brush proxy, and dry grass clump proxy. The foliage materials include
+  per-instance color variation so repeated instances do not read as copied
+  engine primitives.
 - Wood, fiber, stone, and freshwater actors receive distinct first-pass
   materials.
 - Investor-facing asset variation actors add additional tree canopies/trunks,
@@ -50,7 +53,10 @@ space.
 `Scripts/verify_ground_zero_natural_environment_pass.py` checks that the
 materials exist, the landscape uses the terrain material, the foliage actor has
 the expected investor-facing instance counts and material assignments, and
-resource/water actors are visually dressed. It also checks that the terrain
+resource/water actors are visually dressed. It also checks that foliage no
+longer points at `/Engine/BasicShapes` or template meshes, that the three
+coastal-scrub vegetation assets are assigned, and that tree, shrub, and grass
+components have explicit cull distances for performance. It also checks that the terrain
 material contains procedural color breakup rather than a flat constant color:
 noise, blend, and coastal-scrub color-vector expression families must be present
 in the saved material package. It also checks the asset variation