Retry
/retry Tier 1
Retry transient failures with a configurable backoff strategy. Three flavors: Retry (transient-only via xerr.IsTransient), RetryIf (custom predicate), RetryAll (any non-nil error — idempotent jobs only).
Signature
action contract.Retry(maxRetry int, backoff func(int) time.Duration) *Builder[Req, Res]