Add main menu, WebSocket API demo, and multi-scene game hub.

Replace the single-entry Pong flow with a menu launcher, a per-client API demo on :8081/ws with stream controls and tap flash feedback, and bump the viewport to 1920×1080.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/config.gd

@@ -0,0 +1,19 @@
+extends Control
+
+const MENU_SCENE := "res://scenes/menu.tscn"
+const WS_URL := "ws://localhost:9090/ws"
+
+@onready var back_button: Button = $UiLayer/BackButton
+@onready var ws_url_label: Label = $UiLayer/Panel/WSUrlLabel
+@onready var viewport_label: Label = $UiLayer/Panel/ViewportLabel
+
+
+func _ready() -> void:
+	back_button.pressed.connect(_return_to_menu)
+	ws_url_label.text = "WebSocket: %s" % WS_URL
+	var size := get_viewport_rect().size
+	viewport_label.text = "Viewport: %d × %d" % [int(size.x), int(size.y)]
+
+
+func _return_to_menu() -> void:
+	get_tree().change_scene_to_file(MENU_SCENE)