Process an Event Queue That Arrives Out of Order

The problem, from first principles

A real-time agent's events don't always arrive in the order they were produced -- network jitter, retries, or multiple concurrent producers (a tool result racing a token chunk) can deliver them out of sequence. Processing them in arrival order rather than in the order they actually happened can render a response with its own steps scrambled.

The task

Write process_event_queue(events, handlers). Each event is (timestamp, event_type, payload). Sort by timestamp first, then for each event whose event_type has an entry in handlers (a format string with one {} placeholder), append handlers[event_type].format(payload) to the result. Skip event types with no handler.