Function run_enable_with 

pub fn run_enable_with(
    project_root: &Path,
    home: &Path,
    opts: &ToggleOpts,
    cmd: &McpCommand,
    ext: &Externals,
) -> Result<String, CliError>

Like run_enable, with the server command and the external environment supplied by the caller. Tests use this to stay deterministic and offline.