fix: repair jajce beauty asset pipeline

tests/jajce_world_scaffold_test.gd

@@ -11,6 +11,8 @@ func _run() -> void:
 	var camera := Camera3D.new()
 	camera.current = true
 	root.add_child(camera)
+	var configured_assets: Terrain3DAssets = load("res://terrain/jajce/assets.tres")
+	var configured_texture_count := configured_assets.get_texture_count()
 
 	var world: Node3D = load("res://world/jajce/JajceWorld.tscn").instantiate()
 	root.add_child(world)
@@ -25,12 +27,26 @@ func _run() -> void:
 		"Terrain3D should use dedicated Jajce data"
 	)
 	_check(
-		terrain.assets.get_texture_count() >= 3,
+		configured_texture_count == 6,
 		(
-			"Jajce terrain should expose at least three materials (found %s)"
-			% terrain.assets.get_texture_count()
+			"Jajce terrain should define the bounded six-material palette (found %s)"
+			% configured_texture_count
 		)
 	)
+	var texture_contract_valid := true
+	for texture_index in configured_texture_count:
+		var texture_asset: Terrain3DTextureAsset = configured_assets.get_texture(texture_index)
+		texture_contract_valid = (
+			texture_contract_valid
+			and texture_asset.albedo_texture != null
+			and texture_asset.normal_texture != null
+			and texture_asset.albedo_texture.get_image().has_mipmaps()
+			and texture_asset.normal_texture.get_image().has_mipmaps()
+		)
+	_check(
+		texture_contract_valid,
+		"All Terrain3D texture assets should provide matching mipmapped maps"
+	)
 	_check(
 		absf(terrain.data.get_height(Vector3.ZERO)) < 0.1,
 		"Central gameplay area should remain level for current navigation"
@@ -52,6 +68,11 @@ func _run() -> void:
 		world.has_node("WaterRoot/WaterfallMist"),
 		"WaterRoot should include waterfall mist particles"
 	)
+	var waterfall_mist: GPUParticles3D = world.get_node("WaterRoot/WaterfallMist")
+	_check(
+		waterfall_mist.draw_pass_1 != null,
+		"Waterfall mist particles should have visible billboard geometry"
+	)
 	_check(world.has_node("WaterRoot/RiverSurface"), "WaterRoot should include a river surface")
 	var environment: Environment = (
 		(world.get_node("WorldEnvironment") as WorldEnvironment).environment
@@ -67,6 +88,9 @@ func _run() -> void:
 	var smoke_count := 0
 	for suffix in ["House_01", "House_02", "House_03"]:
 		if world.has_node("VillageRoot/%s/Smoke" % suffix):
+			var smoke: GPUParticles3D = world.get_node("VillageRoot/%s/Smoke" % suffix)
+			if smoke.draw_pass_1 == null:
+				continue
 			smoke_count += 1
 	_check(
 		smoke_count >= 2,