Optional ReadonlymessageTrimmed and length-capped excerpt of the caught error's message. The
archiver caps this at 1 KB so a runaway stack-as-message cannot bloat the
summary; full message + stack live in {phase}.error.json.gz.
Optional ReadonlynameError constructor name (Error, TypeError, AutoBeTimeoutError,
etc.). Useful when the caught failure was a typed AutoBE error whose name
itself carries information beyond the message.
Compact error excerpt carried on IPhaseState.error. Mirrors the minimum-useful subset of the on-disk
{phase}.error.json.gzpayload so a summary reader can read failure context without loading the compressed sidecar.