refactor: behaviour collector Count and indexer accessors added

Engine.Core/ActiveBehaviourCollector.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Collections;
 using System.Collections.Generic;
 
@@ -16,7 +15,6 @@ public class ActiveBehaviourCollector<T> : IBehaviourCollector<T> where T : clas
     protected readonly List<T> activeBehaviours = new(32);
     protected readonly Dictionary<IActive, T> monitoringActiveToBehaviour = new(32);
 
-    public IReadOnlyList<T> Behaviours => activeBehaviours;
     public IUniverse Universe { get; private set; } = null!;
 
     public ActiveBehaviourCollector() { }
@@ -117,4 +115,7 @@ public class ActiveBehaviourCollector<T> : IBehaviourCollector<T> where T : clas
         OnUnassigned?.Invoke(this);
         return true;
     }
+
+    public int Count => activeBehaviours.Count;
+    public T this[System.Index index] => activeBehaviours[index];
 }