* feat: add dedicated StopEvent subclasses for workflow termination scenarios
Add WorkflowTerminationEvent base class and specific subclasses to provide
detailed information when workflows end abnormally:
- WorkflowTimedOutEvent: Published when workflow exceeds timeout, includes
timeout duration and list of active steps
- WorkflowCancelledEvent: Published when workflow is cancelled by user
- WorkflowFailedEvent: Published when a step fails permanently, includes
step name, exception type, and exception message
These events replace the empty StopEvent() instances that were previously
published, allowing consumers to understand why a workflow ended and take
appropriate action.
Closes: issue about providing exception information in StopEvent
* refactor: simplify termination events to inherit directly from StopEvent
* chore: add changeset
* feat: add traceback and fully qualified exception type to WorkflowFailedEvent
* feat: add retry info (attempts, elapsed_seconds) to WorkflowFailedEvent
Also fixes a bug where step_function.py used time.monotonic() instead of
time.time(), causing incompatible timestamps with first_attempt_at.
* fix lints/locks
* docs: add workflow termination events to streaming docs
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Co-authored-by: Claude <noreply@anthropic.com>
Adrian Lyjak