Preserve approved pixel tower prototype as development baseline

autoload/event_bus.gd

@@ -0,0 +1,13 @@
+extends Node
+
+signal layer_changed(layer: int)
+signal facility_selected(facility_id: StringName)
+signal notification_requested(message: String, severity: int)
+signal simulation_event_recorded(event_name: StringName, payload: Dictionary)
+
+enum Severity {
+	INFO,
+	ECONOMY,
+	WARNING,
+	CRITICAL,
+}