Refactor gameplay menus into owned scenes

ui/menus/PlanningMenu.gd

@@ -0,0 +1,25 @@
+extends "res://ui/menus/ModalMenu.gd"
+
+@onready var panel: Control = $Panel
+@onready var status: Label = $StatusLabel
+
+
+func _ready() -> void:
+	super._ready()
+	panel.changed.connect(refresh)
+
+
+func open_menu() -> void:
+	super.open_menu()
+	refresh()
+
+
+func refresh() -> void:
+	panel.refresh()
+	var short: PackedStringArray = PackedStringArray()
+	for vessel_type in GameState.planned_vessel_types():
+		var missing: int = GameState.vessel_shortfall(String(vessel_type))
+		if missing > 0:
+			short.append("%d %s" % [missing, GameState.vessel_name(String(vessel_type))])
+	status.text = "Every standing order is met or already being built" if short.is_empty() \
+		else "Short: %s" % ", ".join(short)