Fix JSON Marshal for StreamingMessageEvent

[Gaojianli]

1. The status enum for status_updateshould be status-update
2. The final args is missing in NewTaskStatusUpdateEvent
3. The MarshalJSON is using a pointer receiver, while will casue this function not be called. The SSE json data is wrong(the right screenshot):
   

[github-actions]

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[Gaojianli]

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[Gaojianli]

The test failed... but i have no idea how to fix it

[hyprh]

The test failed... but i have no idea how to fix it

Hi, you could try keep the pointer receiver of unmarshal, I think it should be work.

func (r *StreamingMessageEvent) UnmarshalJSON(data []byte) error { -> func (r StreamingMessageEvent) UnmarshalJSON(data []byte) error {

[Gaojianli]

The test failed because of the TaskEvent
https://github.com/Gaojianli/trpc-a2a-go/blob/45472e83f76beeb62a9503139da3e7b1e73a422b/server/server.go#L769-L771

[hyprh]

The test failed because of the TaskEvent https://github.com/Gaojianli/trpc-a2a-go/blob/45472e83f76beeb62a9503139da3e7b1e73a422b/server/server.go#L769-L771

I think a temporary solution is add Event interface to TaskEvent, and handle TaskEvent in sendSSEEvent manually.

We will try to remove StreamingTask and TaskEvent in further version.

[hyprh]

Would you mind submitting this modification for us? Or let's get this CR approved first and then we fix it later.

[Gaojianli]

Would you mind submitting this modification for us? Or let's get this CR approved first and then we fix it later.

OK, please merge this.