Function run_complete_subagent_task 

pub async fn run_complete_subagent_task(
    recipe: Recipe,
    task_config: TaskConfig,
    return_last_only: bool,
    session_id: String,
    images: Option<Vec<ImageData>>,
    cancellation_token: Option<CancellationToken>,
) -> Result<String, Error>

Standalone function to run a complete subagent task with output options