Fix assistant messages conversions in OpenAiResponseAgent chat history

Author: jurepurgar

dotnet/src/Agents/OpenAI/Extensions/ChatContentMessageExtensions.cs

@@ -44,8 +44,10 @@ public static IEnumerable<ThreadInitializationMessage> ToThreadInitializationMes
     public static ResponseItem ToResponseItem(this ChatMessageContent message)
     {
         var items = message.Items;
-        IEnumerable<ResponseContentPart> contentParts = items.Select(item => item.ToResponseContentPart());
-        return message.Role.Label.ToUpperInvariant() switch
+        var roleLabel = message.Role.Label.ToUpperInvariant();
+
+        IEnumerable<ResponseContentPart> contentParts = items.Select(item => item.ToResponseContentPart(roleLabel == "ASSISTANT"));
+        return roleLabel switch
         {
             "SYSTEM" => ResponseItem.CreateSystemMessageItem(contentParts),
             "USER" => ResponseItem.CreateUserMessageItem(contentParts),

dotnet/src/Agents/OpenAI/Extensions/KernelContentExtensions.cs

@@ -10,21 +10,23 @@ namespace Microsoft.SemanticKernel.Agents.OpenAI;
 /// </summary>
 internal static class KernelContentExtensions
 {
-    internal static ResponseContentPart ToResponseContentPart(this KernelContent content)
+    internal static ResponseContentPart ToResponseContentPart(this KernelContent content, bool isOutput = false)
     {
         return content switch
         {
-            TextContent textContent => textContent.ToResponseContentPart(),
+            TextContent textContent => textContent.ToResponseContentPart(isOutput),
             ImageContent imageContent => imageContent.ToResponseContentPart(),
             BinaryContent binaryContent => binaryContent.ToResponseContentPart(),
             FileReferenceContent fileReferenceContent => fileReferenceContent.ToResponseContentPart(),
             _ => throw new NotSupportedException($"Unsupported content type {content.GetType().Name}. Cannot convert to {nameof(ResponseContentPart)}.")
         };
     }
 
-    internal static ResponseContentPart ToResponseContentPart(this TextContent content)
+    internal static ResponseContentPart ToResponseContentPart(this TextContent content, bool isOutput)
     {
-        return ResponseContentPart.CreateInputTextPart(content.Text);
+        return isOutput ?
+            ResponseContentPart.CreateOutputTextPart(content.Text, []) : 
+            ResponseContentPart.CreateInputTextPart(content.Text);
     }
 
     internal static ResponseContentPart ToResponseContentPart(this ImageContent content)