.Net: Extend sample to show how to use MCP Tools from an Agent

[markwallace-microsoft]

Motivation and Context

Extend the sample to show how to use MCP Tools from an Agent.

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[RogerBarreto]

May be simpler just use the ToString() implicit here.

Suggested change

	ChatMessageContent response = await agent.InvokeAsync("Summarize the last four commits to the microsoft/semantic-kernel repository?").FirstAsync();
	Console.WriteLine($"\n\nResponse from GitHubAgent:\n{response.Content}");
	var response = await agent.InvokeAsync("Summarize the last four commits to the microsoft/semantic-kernel repository?").FirstAsync();
	Console.WriteLine($"\n\nResponse from GitHubAgent:\n{response}");

Suggested change

	ChatMessageContent response = await agent.InvokeAsync("Summarize the last four commits to the microsoft/semantic-kernel repository?").FirstAsync();
	Console.WriteLine($"\n\nResponse from GitHubAgent:\n{response.Content}");
	ChatMessageContent response = await agent.InvokeAsync("Summarize the last four commits to the microsoft/semantic-kernel repository?").FirstAsync();
	Console.WriteLine($"\n\nResponse from GitHubAgent:\n{response.Content}");