#214 Replay: Implement Compensation/Saga Pattern Support

## Problem No mechanism to define compensating tasks for rollback scenarios. ## Industry Standard Temporal and Cadence support compensating tasks automatically. ## Use Case Financial transactions requiring rollback: ```python # Current: No way to auto-rollback ctx.step("debit_account", debit, amount) # If later step fails, no automatic credit_account(amount) ``` ## Impact - Banks cannot safely implement financial workflows - Manual saga pattern implementation error-prone - Critical for production-grade reliability ## Solution Options 1. Saga framework with compensation registry 2. Decorator-based: `@compensate(credit_account)` 3. Context-based: `ctx.step(..., compensation=fn)` ## Effort: Large (requires saga pattern framework)