A numeric engine option: fallback when undefined, else an integer in 0..max,
or a JobsucheValidationError (Invalid <name>: ...). A negative, NaN or
fractional value would otherwise silently disable the timeout or the size cap,
and an unbounded maxRetries would keep retrying. Exported so side fetchers
(obtainKey) apply the same rule.
A numeric engine option:
fallbackwhen undefined, else an integer in 0..max, or a JobsucheValidationError (Invalid <name>: ...). A negative, NaN or fractional value would otherwise silently disable the timeout or the size cap, and an unbounded maxRetries would keep retrying. Exported so side fetchers (obtainKey) apply the same rule.