.NET: Fixes AgentWithHostedMCP chat fails: ErrorHTTP 404 (: 404) Resource not found

[rogerbarreto]

Motivation and Context

• Fixes Python: .NET: AgentWithHostedMCP chat fails: ErrorHTTP 404 (: 404) Resource not found #3195

[Copilot]

Pull request overview

Updates the AgentWithHostedMCP .NET sample to align with newer Azure AI Agent Server / Azure OpenAI packages and the current Microsoft.Extensions.AI.OpenAI integration approach, addressing the reported hosted MCP chat failure.

Changes:

• Bumps Azure.AI.AgentServer.AgentFramework and Azure.AI.OpenAI package versions.
• Moves the sample to Microsoft.Extensions.AI.OpenAI 10.3.0 and adjusts the agent creation pipeline to convert the Responses client into an IChatClient.
• Improves the sample HTTP request file formatting by adding the standard blank line between headers and JSON bodies.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
dotnet/samples/HostedAgents/AgentWithHostedMCP/run-requests.http	Adds blank lines between headers and bodies to ensure HTTP client tooling parses requests correctly.
dotnet/samples/HostedAgents/AgentWithHostedMCP/Program.cs	Updates the Responses client flow to AsIChatClient() before creating the agent; removes an unused/now-unneeded using.
dotnet/samples/HostedAgents/AgentWithHostedMCP/AgentWithHostedMCP.csproj	Updates package versions and removes now-unneeded OpenAI-specific Agent Framework package reference in favor of Microsoft.Extensions.AI.OpenAI 10.3.0.

[westey-m]

Is this sample using some really old packages? We don't have a sync CreateAIAgent anymore after all, especially not on IChatClient. It should now all be AsAIAgent right? Also, why would we not use the extension method on the responses client directly. It should be equivalent to the one on IChatClient, right?