Fix pydantic-ai deprecation warning: mcp_servers -> toolsets

[zzstoatzz]

Summary

Fixes the deprecation warning from pydantic-ai by updating the parameter name from mcp_servers to toolsets when instantiating pydantic-ai's Agent.

Closes #1205

Problem

The test suite was showing this deprecation warning:

tests/ai/test_mcp.py::test_mcp_git_server_tool_usage_and_output
  /home/runner/work/marvin/marvin/.venv/lib/python3.11/site-packages/pydantic_ai/agent/__init__.py:310: 
  DeprecationWarning: `mcp_servers` is deprecated, use `toolsets` instead

Solution

Updated the single location where Marvin passes MCP servers to pydantic-ai's Agent constructor:

• Changed agent_kwargs["mcp_servers"] to agent_kwargs["toolsets"] in src/marvin/agents/agent.py:209

This is an internal implementation detail only. Marvin's public API remains unchanged - users continue to use mcp_servers when creating Marvin Agents.

Testing

✅ Verified the deprecation warning exists on main branch
✅ Confirmed the warning is eliminated with this fix
✅ All MCP-related tests pass:

• tests/ai/test_mcp.py
• tests/agents/test_mcp_integration.py

Backwards Compatibility

This change maintains full backwards compatibility:

• Marvin's public API is unchanged
• Users continue to pass mcp_servers to Marvin's Agent class
• Only the internal pydantic-ai integration is updated

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

This PR fixes a deprecation warning from pydantic-ai by updating the parameter name used internally when passing MCP servers to pydantic-ai's Agent constructor.

• Updates internal parameter from mcp_servers to toolsets to align with pydantic-ai's current API
• Maintains full backwards compatibility for Marvin's public API
• Eliminates deprecation warning in test suite

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}