Cloudflare Workflow Saga Rollback

A Cloudflare Workflow that compensates instead of unwinding by hand. Each side-effecting step.do registers a WorkflowStepRollbackOptions handler with its own rollbackConfig retry budget, so a terminal failure refunds the charge and revokes the seats in reverse step-start order. Includes a dynamic retries.delay function that reads the provider's Retry-After out of the error, NonRetryableError fail-fast on 402/409, sensitive step output, cron-versus-user detection through WorkflowEvent.schedule, and a control-plane Worker doing terminate({ rollback: true }) and restart({ from }).