Function materialize_credential_file 

pub fn materialize_credential_file(
    key_name: &str,
    content: &str,
    wipe_on_drop: bool,
    ati_dir: &Path,
) -> Result<CredentialFile, CliError>

Materialize a keyring secret as a file on disk with 0600 permissions.

In dev mode (wipe_on_drop = false), uses a stable path so repeated runs reuse the same file. In prod mode (wipe_on_drop = true), appends a random suffix so concurrent invocations don’t collide.