fix: resolve asyncio event loop conflicts in MCP server registration

[eranco74]

Description

Add async/await support for LlamaStackAsLibraryClient to prevent
"Cannot run event loop while another loop is running" RuntimeError.

Changes:
- Introduce register_mcp_servers_async() for async MCP server registration
- Refactor MCP registration logic into separate sync/async helper functions
- Use async client methods (client.async_client) for library clients
to avoid "Cannot run event loop while another loop is running" errors
- Add async tests for library client configuration

The LlamaStackAsLibraryClient requires async initialization, but the previous
sync implementation caused event loop conflicts. This change provides dual
support for both service clients (sync) and library clients (async).

Type of change

• Refactor
• New feature
• Bug fix
• CVE fix
• Optimization
• Documentation Update
• Configuration Update
• Bump-up service version
• Bump-up dependent library
• Bump-up library or tool used for development (does not change the final image)
• CI configuration change
• Konflux configuration change
• Unit tests improvement
• Integration tests improvement
• End to end tests improvement

Related Tickets & Documents

• Related Issue #
  Fixes RuntimeError when configuration.llama_stack.use_as_library_client = true

• Closes #

Checklist before requesting a review

• I have performed a self-review of my code.
• PR has passed all pre-merge test jobs.
• If it is a core feature, I have added thorough tests.

Testing

• Please provide detailed steps to perform tests related to this code change.
• How were the fix/results from this change verified? Please provide relevant screenshots or results.

[tisnik]

it looks ok, but would like @manstis to test it if possible. @manstis PLEASE

[manstis]

LGTM 👍

Minor comment about consistency of the code-flow.

[manstis]

IMO it'd be better to get the client here too; to be consistent with the async approach.

async def register_mcp_servers_async(
    logger: Logger, configuration: Configuration
) -> None:
    """Register Model Context Protocol (MCP) servers with the LlamaStack client (async)."""
    if configuration.llama_stack.use_as_library_client:
        # Library client - use async interface
        # config.py validation ensures library_client_config_path is not None
        # when use_as_library_client is True
        config_path = cast(str, configuration.llama_stack.library_client_config_path)
        client = LlamaStackAsLibraryClient(config_path)
        await client.async_client.initialize()

        await _register_mcp_toolgroups_async(
            client.async_client, configuration.mcp_servers, logger
        )
    else:
        # Service client - use sync interface
        client = get_llama_stack_client(configuration.llama_stack)
    
        _register_mcp_toolgroups_sync(client, configuration.mcp_servers, logger)

[manstis]

Delete this if doing the above proposal.

[eranco74]

I added it to make the tests a bit clearer (async when not using as a library).