Turn dev mode into sandbox menu

tests/_dev_menu_preview.gd

@@ -0,0 +1,28 @@
+extends Node2D
+
+# Visual-only phone preview for the editor sandbox panel. It builds only the
+# fleet and the menu; loading Main also schedules infinite-world population,
+# which is wasted behind this opaque panel and painfully slow in softpipe.
+#
+#   bash tests/screenshot.sh res://tests/_dev_menu_preview.tscn /tmp/dev_menu.png 4 720x1280
+
+const FLEET = preload("res://vessels/Fleet.gd")
+const DEV_MENU = preload("res://ui/menus/DevMenu.tscn")
+
+
+func _ready() -> void:
+	GameState.start_dev_game()
+	GameState.dev_unlock_all_skills()
+	var fleet: Node = FLEET.new()
+	add_child(fleet)
+	fleet.spawn_ships(4, Vector2.ZERO, PackedStringArray([
+		GameState.VESSEL_INTERCEPTOR,
+		GameState.VESSEL_SHIELD,
+		GameState.VESSEL_GAS_BOMBER,
+		GameState.VESSEL_LASER,
+	]))
+	var layer := CanvasLayer.new()
+	add_child(layer)
+	var menu: Control = DEV_MENU.instantiate()
+	layer.add_child(menu)
+	menu.open_for(fleet)