adds emission sequencing, parent-child event hierarchy with scope management, and integrates both into the event bus. introduces flush() for deterministic handling, resets emission counters for test isolation, and adds chain tracking via previous_event_id/triggered_by_event_id plus context variables populated during emit and listener execution. includes tracing listener typing/sorting improvements, safer tool event pairing with try/finally, additional stack checks and cache-hit formatting, context isolation fixes, cassette regen/decoding, and test updates to handle vcr race conditions and flaky behavior.