.NET: [Bug]: Need a way to send async task status by using the push notification feature

### Description

Package version - 1.0.0-preview.260304.1
We are having an orchestration engine which we are exposing as an agent (using A2A) to the outside world so that other external agent can communicate with our engine.
Now, as per our current implementation, an external agent sends an agent message which contains message id , context id, parts (inside parts we have a prompt), metadata, and all the required parameters to our agent. Now our agents receive the message; it generates a response and makes agent task status as completed and returns the final agent task with LLM response.

`Sample External Agent request message -
{
"jsonrpc": "2.0",
"method": "message/send",
"params": {
"message": {
"kind": "agentMessage",
"role": "user",
"messageId": "550e8400-e29b-41d4-a716-446655440000",
"contextId": "550e8400-e29b-41d4-a716-446655440001",
"parts": [
{
"kind": "text",
"text": "hi"
}
],
"metadata": {
"product": "productName",
"persona": "perosnaName"
}
}
},
"id": 1
}

`
Now we wanted to explore the ways where before completing the agent task if we can somehow return the task status or some agent message. Does this package offer any way to do this ? And how we can use Server Sent Events in this use case so that external agents don't have to wait for the final response ?
We were thinking a way to send the task status by using the push notification feature, now from the below portion of source code we found out TaskManager UpdateStatusAsync method is yet to implement this.

### Code Sample

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### Error Messages / Stack Traces

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### Package Versions

Package version - 1.0.0-preview.260304.1

### .NET Version

_No response_

### Additional Context

_No response_