Report embedding failures with a clear cause

app/MindWork AI Studio/Tools/Services/FileEnumerationResult.cs

@@ -12,8 +12,8 @@ public sealed class FileEnumerationResult
 
     public void AddFailure(string filePath, string reason)
     {
-        this.Failures.Add(new DataSourceEmbeddingFailure(filePath, reason));
+        this.Failures.Add(new DataSourceEmbeddingFailure(filePath, reason, DateTimeOffset.UtcNow));
         this.FailedFiles = this.Failures.Count;
         this.LastError = reason;
     }
-}
+}