Get ETL process status by process UUID

Poll until the process reaches a terminal outcome. If statusCode is "finished", the run succeeded. If statusCode is "error", "aborted", or "killed": when followupProcessUuid is set, that is not a terminal failure — continue with GET /etl/v1/process/status/{followupProcessUuid}; when followupProcessUuid is null, treat the run as a terminal failure. For any other statusCode, keep polling the same process UUID. Auto-retries after failure return statusCode "error" with followupProcessUuid pointing at the retry process; retries can chain if a followup also fails.