A system initialization message from the CLI.
@type t() :: %AmpSdk.Types.SystemMessage{ cwd: String.t(), extra: map(), mcp_servers: [AmpSdk.Types.MCPServerStatus.t()], session_id: String.t(), subtype: String.t(), tools: [String.t()], type: String.t() }
@spec parse(map() | t()) :: {:ok, t()} | {:error, {:invalid_system_message, CliSubprocessCore.Schema.error_detail()}}
@spec parse!(map() | t()) :: t()