Fix TapADN ad lifecycle callbacks

DirichletMediation/Runtime/DirichletAdTypes.cs

@@ -752,6 +752,11 @@ namespace Dirichlet.Mediation
         /// </summary>
         public event Action Closed;
 
+        /// <summary>
+        /// Raised when the native layer reports that a loaded ad failed to show.
+        /// </summary>
+        public event Action<DirichletError> ShowFailed;
+
         internal DirichletAd(IDirichletPlatformBridge bridge, DirichletPlatformAdHandle platformHandle, long spaceId)
         {
             this.bridge = bridge ?? throw new ArgumentNullException(nameof(bridge));
@@ -812,6 +817,9 @@ namespace Dirichlet.Mediation
                 case DirichletNativeEventNames.Close:
                     OnClosed();
                     break;
+                case DirichletNativeEventNames.ShowError:
+                    OnShowFailed(nativeEvent.Data);
+                    break;
             }
         }
 
@@ -829,6 +837,13 @@ namespace Dirichlet.Mediation
         {
             Closed?.Invoke();
         }
+
+        protected virtual void OnShowFailed(DirichletNativeEventData data)
+        {
+            var code = data != null && data.Code != 0 ? data.Code.ToString(CultureInfo.InvariantCulture) : "show_error";
+            var message = data?.Message;
+            ShowFailed?.Invoke(new DirichletError(code, string.IsNullOrEmpty(message) ? "Ad failed to show" : message));
+        }
     }
 
     public abstract class DirichletRewardAdBase : DirichletAd
@@ -1085,6 +1100,7 @@ namespace Dirichlet.Mediation
         internal const string Click = "click";
         internal const string Close = "close";
         internal const string Reward = "reward";
+        internal const string ShowError = "show_error";
     }
 
     internal readonly struct DirichletNativeEvent
@@ -1373,4 +1389,3 @@ namespace Dirichlet.Mediation
     }
 }
 
-