feat(samples): AG2 (autogen) + MCP Example Agent Server Implementation

[jtanningbed]

This PR adds a sample agent implementation using AG2 (autogen) framework:

• Demonstrates integration of AG2's AssistantAgent with the A2A protocol
• Showcases interoperability between A2A and Model Context Protocol (MCP)
• Implements a specialized YouTube content agent using mcp-youtube server
• Features structured output processing with OpenAI

This sample highlights how A2A can facilitate connections between diverse agent frameworks, with task requests handled by A2A while specialized processing is managed by framework-specific tools.

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[dmandar]

Thanks for the PR. Can you please resolve conflicts?

[jtanningbed]

Thanks for the PR. Can you please resolve conflicts?

done, thank you!

[qingyun-wu]

Hi, conflicts resolved. @dmandar Could you help review again? Thank you!

[dmandar]

Thanks for the PR. Please fix linter errors.