Fix fall-through (spawn on terrain after collision built) and B&W (assign sky env)

scripts/world/props.gd

@@ -2,18 +2,24 @@ extends Node3D
 ## M0 mood props — a few low-poly trees and rocks built from primitives in code,
 ## so the scene looks "alive" with no imported assets. These are placeholders;
 ## real low-poly models (free asset packs, see docs/ROADMAP.md M0) replace them.
+##
+## place_on(terrain) is called by world.gd once the terrain exists, so each prop
+## sits on the real ground height instead of floating at Y=0.
 
-func _ready() -> void:
-	# A deterministic scattering so it looks intentional, not random each run.
+var _terrain: Node3D
+
+func place_on(terrain: Node3D) -> void:
+	_terrain = terrain
 	var rng := RandomNumberGenerator.new()
 	rng.seed = 42
 	for i in range(18):
 		var x := rng.randf_range(-55.0, 55.0)
 		var z := rng.randf_range(-55.0, 55.0)
+		var y: float = _terrain.sample_height(x, z)
 		if rng.randf() < 0.65:
-			_make_tree(Vector3(x, 0, z), rng)
+			_make_tree(Vector3(x, y, z), rng)
 		else:
-			_make_rock(Vector3(x, 0, z), rng)
+			_make_rock(Vector3(x, y, z), rng)
 
 func _make_tree(pos: Vector3, rng: RandomNumberGenerator) -> void:
 	var root := Node3D.new()