test(scenes): ✅ Add viewport proof test scene with test script and assets for viewport behavior validation

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

src/game/engine/scenes/tests/viewport_proof.gd

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+extends Node2D
+## Viewport Window Manager Proof Scene.
+## Generates a hex map, instantiates the WorldMap scene, then exercises
+## ViewportWindowManager: splits the panel horizontally and opens a floating
+## window. Self-capturing: saves screenshot and quits.
+
+const MapGeneratorScript: GDScript = preload(
+	"res://engine/src/generation/map_generator.gd"
+)
+const GameMapScript: GDScript = preload("res://engine/src/map/game_map.gd")
+const PlayerScript: GDScript = preload("res://engine/src/entities/player.gd")
+const WorldMapScene: PackedScene = preload(
+	"res://engine/scenes/world_map/world_map.tscn"
+)
+
+const OUTPUT_DIR: String = "user://screenshots"
+
+var _captured: bool = false
+var _screenshot_name: String = "viewport_proof"
+
+
+func _ready() -> void:
+	RenderingServer.set_default_clear_color(Color(0.06, 0.05, 0.04))
+	get_viewport().size = Vector2i(1920, 1080)
+	DisplayServer.window_set_size(Vector2i(1920, 1080))
+
+	var env_name: String = OS.get_environment("SCREENSHOT_NAME")
+	if not env_name.is_empty():
+		_screenshot_name = env_name
+
+	DataLoader.load_theme("age-of-dwarves")
+
+	await get_tree().process_frame
+
+	_setup_game_state()
+	_add_world_map()
+
+	# Wait 2 frames for the WorldMap scene to fully initialize
+	await get_tree().process_frame
+	await get_tree().process_frame
+
+	_exercise_viewport_manager()
+
+	# Wait 1 more frame for viewport changes to render
+	await get_tree().process_frame
+
+	# Additional frames to let split panels and floating window settle
+	for _i: int in range(8):
+		await get_tree().process_frame
+
+	_capture_and_quit()
+
+
+func _setup_game_state() -> void:
+	print("=== Viewport Proof ===")
+
+	var settings: Dictionary = {
+		"map_size": "duel",
+		"map_type": "continents",
+		"seed": 42,
+		"num_players": 2,
+		"map_wrap": "cylinder",
+	}
+
+	GameState.initialize_game(settings)
+	GameState.map_seed = 42
+
+	var generator: RefCounted = MapGeneratorScript.new()
+	var game_map: GameMapScript = generator.generate(settings)
+
+	var primary: Dictionary = GameState.get_primary_layer()
+	primary["map"] = game_map
+
+	# Create a player so WorldMap can render
+	var player: RefCounted = GameState.create_player("Proof Player", "dwarf", true)
+	print(
+		"Map: %dx%d, duel, seed 42 | Player: %s (index %d)"
+		% [game_map.width, game_map.height, player.player_name, player.index]
+	)
+
+
+func _add_world_map() -> void:
+	var world_map: Node2D = WorldMapScene.instantiate()
+	world_map.name = "WorldMap"
+	add_child(world_map)
+	print("WorldMap scene instantiated")
+
+
+func _exercise_viewport_manager() -> void:
+	var world_map: Node2D = get_node_or_null("WorldMap")
+	if world_map == null:
+		push_error("ViewportProof: WorldMap node not found")
+		return
+
+	var vwm: Control = world_map.get_node_or_null("ViewportWindowManager")
+	if vwm == null:
+		push_error("ViewportProof: ViewportWindowManager not found")
+		return
+
+	# Exercise split panel: make it visible and split horizontally
+	var split_container: Control = vwm.get_split_panel_container()
+	split_container.visible = true
+	split_container.split_focused_horizontal()
+	print("Split panel: split_focused_horizontal() called")
+
+	# Exercise floating window: open one at the map center
+	vwm.open_floating_window(Vector2(400, 300), 1)
+	print("Floating window: opened at (400, 300), layer_mask=1")
+
+
+func _capture_and_quit() -> void:
+	if _captured:
+		return
+	_captured = true
+
+	DirAccess.make_dir_recursive_absolute(
+		ProjectSettings.globalize_path(OUTPUT_DIR)
+	)
+	var image: Image = get_viewport().get_texture().get_image()
+	if image == null:
+		push_error("ViewportProof: Failed to get viewport image")
+		get_tree().quit(1)
+		return
+
+	var timestamp: String = (
+		Time.get_datetime_string_from_system()
+		.replace(":", "-")
+		.replace("T", "_")
+	)
+	var rel_path: String = "%s/%s_%s.png" % [OUTPUT_DIR, _screenshot_name, timestamp]
+	var abs_path: String = ProjectSettings.globalize_path(rel_path)
+	var err: Error = image.save_png(abs_path)
+
+	if err == OK:
+		print("SCREENSHOT_PATH:%s" % abs_path)
+		print(
+			"Screenshot: %dx%d saved to %s"
+			% [image.get_width(), image.get_height(), abs_path]
+		)
+	else:
+		push_error("ViewportProof: Save failed: %s" % error_string(err))
+
+	get_tree().quit()

src/game/engine/scenes/tests/viewport_proof.gd.uid

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+uid://x1dj50wpjio0

src/game/engine/scenes/tests/viewport_proof.tscn

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+[gd_scene load_steps=2 format=3 uid="uid://vp7proof1"]
+
+[ext_resource type="Script" path="res://engine/scenes/tests/viewport_proof.gd" id="1_script"]
+
+[node name="ViewportProof" type="Node2D"]
+script = ExtResource("1_script")