Run a transfer fan-out. Returns a success envelope when the orchestration
completes (even if every target failed); throws only for pre-flight failures
(bad request shape, missing --out-dir, CDB decrypt, unconfirmed write) the
caller renders as an outer error via buildTransferFanoutErrorEnvelope.
Run a
transferfan-out. Returns a success envelope when the orchestration completes (even if every target failed); throws only for pre-flight failures (bad request shape, missing--out-dir, CDB decrypt, unconfirmed write) the caller renders as an outer error via buildTransferFanoutErrorEnvelope.