Error Handling
status=error includes code and message.
Common examples:
-80: operation not supported-29: invalid request parameters/body-16: original transaction not found-15: transaction not found-47: unsupported currency-21: cancelled by user-20: declined-54: card input timeout-3: generic send/processing error-100: critical version update required-101: application blocked
Recommendation: handle all unknown codes as non-retriable by default, then fallback to /check for state recovery when financial status is
uncertain.