Function generate_command_files 

pub fn generate_command_files(
    out_dir: &str,
    cmd_base_dir: &str,
    app: &Command,
) -> Result<()>

Ported from GenerateCommandFiles. Writes one markdown file per visible top-level command into out_dir, plus an _index.md listing all commands. cmd_base_dir is the directory containing per-command packages (e.g. "cmd"); a DOC.md file found at cmd_base_dir/{normalized_name}/DOC.md is appended to each command’s Description section.