Python: MCP sample bugbash fixes

[giles17]

Motivation and Context

Fixes errors from two MCP samples found during bugbash

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR fixes API usage errors in two MCP sample files discovered during a bugbash. The changes correct parameter names and values in the get_mcp_tool() method call to match the actual API signature, and add the standard if __name__ == "__main__" pattern to make one sample executable.

Changes:

• Fixed get_mcp_tool() parameter names from internal dict keys (server_label, server_url, require_approval) to correct API parameters (name, url, approval_mode)
• Fixed approval_mode value from "never" to "never_require"
• Added if __name__ == "__main__" block to mcp_api_key_auth.py for direct execution

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/samples/02-agents/mcp/mcp_github_pat.py	Corrects get_mcp_tool() parameters from internal dict keys to proper API parameters (server_label→name, server_url→url, require_approval→approval_mode) and fixes approval value ("never"→"never_require")
python/samples/02-agents/mcp/mcp_api_key_auth.py	Adds standard if __name__ == "__main__" block with asyncio import to enable direct script execution