Function transaction_directory 

pub fn transaction_directory(
    registry_root: &Path,
    transaction_id: &str,
) -> PathBuf

What: The transaction directory’s names, derived from the registry root and the transaction ID. Why: Callers that build facts before the transaction creates anything use the same names.

In TS you’d write (pseudocode):

transactionPaths({ registryRoot, commonDir, transactionId });