refactor AI system

src/lib/ecs/system/ai/AdvanceExecutor.h

@@ -0,0 +1,11 @@
+#pragma once
+
+class EntityAdmin;
+
+// Moves a ship toward the opposing side when Advance is the winning behavior:
+// player ships advance toward +x (the enemy), enemy ships toward -x (the base).
+class AdvanceExecutor
+{
+public:
+    void execute(EntityAdmin& admin);
+};