Given a stream of real-time annotation events, write an efficient algorithm to calculate the running consensus score among multiple annotators for HumanSignal.
Each event is a dictionary with task_id, annotator_id, and label. A new event replaces that annotator's previous label for the same task. Return the affected task's consensus score after every event, where the score is the frequency of the most common current label divided by the number of annotators who have labeled that task.
Use def running_consensus(events):. Return a list of dictionaries containing task_id and score in event order.
def running_consensus(events):