Implement a pub/sub event emitter

The prompt

You are a software engineer implementing an event system. Build a typed pub/sub event emitter in [LANGUAGE] that supports: strongly typed event names and payloads (using TypeScript discriminated unions or equivalent), synchronous and asynchronous subscribers, once() method for one-time listeners, wildcard subscriptions, subscriber priority ordering, error isolation (one failing subscriber doesn't affect others), memory leak prevention (weak references or explicit cleanup, max listener count warning), unsubscribe by returned handle, and debug mode that logs all events. Include unit tests covering all features including async error isolation.

Language: [LANGUAGE]
Use case: [BROWSER EVENTS / NODE.JS / IN-MEMORY COMMUNICATION BETWEEN MODULES]