Function docker_pull_image 

pub fn docker_pull_image(
    image: &str,
    log_path: Option<&PathBuf>,
) -> (bool, String)

Pull a Docker image with output streaming

When log_path is provided, the image-preparation phase (the docker pull) is also recorded in the session log so the single log file is a gap-free record of everything that ran (issue #138): a Preparing image … marker with a timestamp is written before the pull, each line of pull output is teed into the log as it streams, and an Image ready (<duration>) marker is written afterwards. Without a log_path the behavior is unchanged.

Returns (success, output) tuple