PR Summary

• Addition of a New Configuration File
  A new file named default.nix has been added for adjusting Copilot settings. This includes defining mcpServers and mcpConfigFilePath parameters, and creating a directory for the Copilot configuration with a placeholder for a future setup script.
• Update to Existing Configuration File
  The existing default.nix file located in nix/hm/ai has been updated to include ./copilot in the modules which become activated.
• Adjustments to Client Configuration File
  The mcp-clients.nix file, which manages client configurations, has been modified to have a new copilot client setup. This includes settings for different types, such as local and http.
• Improvements to MCP Configuration File
  The mcp.nix file, overseeing the Master Client Program (MCP), has been enhanced with a mapping for clients. This ensures that copilot and other clients can be selected and configured as needed.
• Modified Checksum for the Rust MCP
  The existing checksum for the aarch64-darwin version of the rust-mcp-filesystem in the rust-mcp-filesystem.nix file has been updated.