[AI] Behavior Actions 시스템 추가

Ultraworked with [Sisyphus](https://github.com/code-yeonggu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

Assets/Scripts/AI/BehaviorActions/Conditions/HasTargetCondition.cs

@@ -0,0 +1,24 @@
+using System;
+using UnityEngine;
+using Unity.Behavior;
+using Unity.Properties;
+using Condition = Unity.Behavior.Condition;
+
+namespace Colosseum.AI.BehaviorActions.Conditions
+{
+    /// <summary>
+    /// 타겟이 존재하는지 확인합니다.
+    /// </summary>
+    [Serializable, GeneratePropertyBag]
+    [NodeDescription(name: "Has Target", story: "Has [Target]", category: "Combat")]
+    public partial class HasTargetCondition : Condition
+    {
+        [SerializeReference]
+        public BlackboardVariable<GameObject> Target;
+
+        public override bool IsTrue()
+        {
+            return Target.Value != null && Target.Value.activeInHierarchy;
+        }
+    }
+}