bug: error TaskStatusUpdateEvent has final=False in event_converter.py #5388

Bug Description

In src/google/adk/a2a/converters/event_converter.py, the _create_error_status_event function creates a TaskStatusUpdateEvent with final=False when the task has failed:

# event_converter.py line ~464
return TaskStatusUpdateEvent(
    task_id=task_id,
    context_id=context_id,
    metadata=event_metadata,
    status=TaskStatus(
        state=TaskState.failed,
        ...
    ),
    final=False,  # <-- BUG: should be True for failed state
)

Expected Behavior

When a task has TaskState.failed, the TaskStatusUpdateEvent should have final=True, because error events represent terminal states — no further events will follow.

The existing implementation in from_adk_event.py already handles this correctly:

# from_adk_event.py line ~154
error_event = TaskStatusUpdateEvent(
    ...
    final=True,  # <-- correct
)

Actual Behavior

Clients/consumers that check the final flag will not know that processing has stopped after a failed status, potentially waiting indefinitely for more events or mishandling the error state.

Fix

Change final=False to final=True in _create_error_status_event in event_converter.py.

Signed-off-by: Cocoon-Break 54054995+kuishou68@users.noreply.github.com