refactor AI system

src/lib/ecs/component/MovementIntentComponent.h

@@ -2,11 +2,12 @@
 
 #include <QVector2D>
 
-// A ship-behavior system writes this each tick before movement runs; the
-// highest-priority write wins. Priority order is fixed globally — see
-// architecture.md "Movement Arbitration".
+// The winning behavior's executor writes this each tick before movement runs.
+// `active` is false when no behavior set a destination (the ship brakes); the
+// score-based selection (see architecture.md "Movement Arbitration") decides
+// which single executor writes here.
 struct MovementIntentComponent
 {
-    int priority;
+    bool      active = false;
     QVector2D target;
 };