.NET: [Bug]: AGUI AGUIMessage -> ChatMessage transformation issue on AGUIToolMessage

[MaciejWarchalowski]

Description

• When transforming AGUIToolMessage to ChatMessage, the ChatMessage.MessageId is null.
• I would expect ChatMessage.MessageId to be populated with AGUIToolMessage.Id

Code Sample

public void AsChatMessages_WithToolMessage_DeserializesResultCorrectly()
    {
        // Arrange
        const string JsonContent = "{\"status\":\"success\",\"value\":42}";
        List<AGUIMessage> aguiMessages =
        [
            new AGUIToolMessage
            {
                Id = "msg1",
                Content = JsonContent,
                ToolCallId = "call_abc"
            }
        ];

        // Act
        List<ChatMessage> chatMessages = aguiMessages.AsChatMessages(AGUIJsonSerializerContext.Default.Options).ToList();

        // Assert
        ChatMessage message = Assert.Single(chatMessages);
        Assert.Equal(ChatRole.Tool, message.Role);
        FunctionResultContent result = Assert.IsType<FunctionResultContent>(message.Contents[0]);
        Assert.Equal("call_abc", result.CallId);
        Assert.NotNull(result.Result);
        Assert.Equal("msg1", message.MessageId); //I would expect this test to pass.
    }

Error Messages / Stack Traces

I would expect `

Assert.Equal("msg1", message.MessageId);

to pass.

Package Versions

Microsoft.Agents.AI.AGUI.Shared

.NET Version

.NET 10

Additional Context

No response