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

[Roger Barreto (rogerbarreto)]

Motivation and Context

• FixesPython: .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.OpenAI10.3.0 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.