NEO-99: Fix Bugbot dead code and GdUnit CI failures

Remove unused ENVIRONMENT preload (environment loads via main.tscn). Update
combat_targets_client_test for three prototype_npc_* rows; auto_free GLB
instances in visual catalog tests to avoid orphan exit code 101.

client/scripts/prototype_district_visual_catalog.gd

@@ -4,8 +4,6 @@ extends Object
 ## Prop GLBs import as a wrapper root plus one child mesh node that still carries baked
 ## world transforms from Blender — see [method normalize_prop_visual].
 
-const ENVIRONMENT: PackedScene = preload("res://assets/district/prototype_district_environment.glb")
-
 const INTERACTABLE_PROPS: Dictionary = {
 	"prototype_terminal": preload("res://assets/district/props/terminal.glb"),
 	"prototype_resource_node_alpha": preload("res://assets/district/props/salvage_alpha.glb"),

client/test/combat_targets_client_test.gd

@@ -30,7 +30,7 @@ class MockHttpTransport:
 		return OK
 
 
-static func _two_target_snapshot_json() -> String:
+static func _prototype_npc_snapshot_json() -> String:
 	return (
 		'{"schemaVersion":1,"targets":['
 		+ '{"targetId":"prototype_npc_melee","maxHp":100,"currentHp":75,"defeated":false},'
@@ -52,7 +52,7 @@ func _make_client(transport: Node) -> Node:
 func test_request_sync_gets_combat_targets_url() -> void:
 	# Arrange
 	var transport := MockHttpTransport.new()
-	transport.body_json = _two_target_snapshot_json()
+	transport.body_json = _prototype_npc_snapshot_json()
 	var c := _make_client(transport)
 	# Act
 	c.call("request_sync_from_server")
@@ -63,7 +63,7 @@ func test_request_sync_gets_combat_targets_url() -> void:
 func test_targets_received_emits_parsed_snapshot() -> void:
 	# Arrange
 	var transport := MockHttpTransport.new()
-	transport.body_json = _two_target_snapshot_json()
+	transport.body_json = _prototype_npc_snapshot_json()
 	var c := _make_client(transport)
 	var got: Array = []
 	c.connect("targets_received", func(snapshot: Dictionary) -> void: got.append(snapshot))
@@ -74,13 +74,13 @@ func test_targets_received_emits_parsed_snapshot() -> void:
 	var snapshot: Dictionary = got[0]
 	var targets: Variant = snapshot.get("targets", null)
 	assert_that(targets is Array).is_true()
-	assert_that((targets as Array).size()).is_equal(2)
+	assert_that((targets as Array).size()).is_equal(3)
 
 
-func test_target_row_returns_alpha_hp_fields() -> void:
+func test_target_row_returns_melee_hp_fields() -> void:
 	# Arrange
 	var transport := MockHttpTransport.new()
-	transport.body_json = _two_target_snapshot_json()
+	transport.body_json = _prototype_npc_snapshot_json()
 	var c := _make_client(transport)
 	var got: Array = []
 	c.connect("targets_received", func(snapshot: Dictionary) -> void: got.append(snapshot))

client/test/prototype_district_visual_catalog_test.gd

@@ -8,6 +8,7 @@ func test_instantiate_prop_clears_baked_child_transform() -> void:
 	var packed: PackedScene = Catalog.INTERACTABLE_PROPS["prototype_resource_node_alpha"]
 	# Act
 	var visual: Node3D = Catalog.instantiate_prop(packed, 0.5)
+	auto_free(visual)
 	# Assert
 	var mesh: Node3D = visual.get_node("IX_SalvageAlpha_Mesh") as Node3D
 	assert_that(mesh.position).is_equal(Vector3.ZERO)
@@ -17,6 +18,7 @@ func test_normalize_prop_visual_grounds_mesh_feet_at_floor() -> void:
 	# Arrange
 	var packed: PackedScene = Catalog.INTERACTABLE_PROPS["prototype_resource_node_alpha"]
 	var visual: Node3D = packed.instantiate() as Node3D
+	auto_free(visual)
 	var mesh: MeshInstance3D = visual.get_node("IX_SalvageAlpha_Mesh") as MeshInstance3D
 	var min_y: float = mesh.get_aabb().position.y
 	# Act