Adds disbursements to an intent that already exists. Every element must carry its own clientReferenceId, unique per settlement account among disbursements; the whole body is validated before anything is created, so a missing, blank or repeated-within-the-body reference is answered 400 and a reference already stored earlier 409. A failure that happens after that validation is reported as a disbursementCreationError inside the 200 response, exactly like POST /api/v1/intents — a payout already accepted by a partner is never rolled back nor retried. The response carries the FULL intent, including the transactions it already had.