Run an execute fan-out. Returns a success envelope when the orchestration
completes (even if every target failed); throws only for pre-flight failures
(invalid command shape, CDB decrypt, unconfirmed write) the caller renders as
an outer error via buildExecuteFanoutErrorEnvelope.
Run an
executefan-out. Returns a success envelope when the orchestration completes (even if every target failed); throws only for pre-flight failures (invalid command shape, CDB decrypt, unconfirmed write) the caller renders as an outer error via buildExecuteFanoutErrorEnvelope.