Design an OS notification platform, working with an AI assistant

Design the notification system of a desktop operating system: the platform piece that lets many applications raise notifications and shows them to the user. Cover the app-facing API, delivery when the app is not running, ordering and grouping, user settings and do-not-disturb, storage, rate limits and abuse from noisy apps. In this round you are expected to use an AI assistant while you work, and the interviewer watches how you use and check it.