When a tool raises an error, both ToolUsageErrorEvent and
ToolUsageFinishedEvent were being emitted. Since both events pop the
event scope stack, this caused the agent scope to be incorrectly popped
along with the tool scope.
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.
