Function write_prepared_record 

pub fn write_prepared_record(
    directory: &Path,
    record: &PreparedRecord,
) -> Result<(), PreparationError>

What: Writes prepared.json exclusively and makes it durable. Why: Recovery reads the prepared record to decide what a dead transaction had prepared.

In TS you’d write (pseudocode):

await writeJournalRecord({ directory, filename: PREPARED_FILENAME, record });