Function prepare_install_target_with_commands 

pub fn prepare_install_target_with_commands(
    conn: &DbConnection,
    name: &str,
    install_dir: &Path,
    package_commands: Option<&str>,
) -> Result<()>

Validate the target install path and clear stale failed state if present.

This variant also checks the command registry so command conflicts fail before the installer payload is downloaded.