Design an iOS Timer App with Consistent State and Asynchronous UI Updates

Clarified Product Assumptions I’ll design a countdown timer with: User actions: start, pause, resume, reset, and set a duration. Elapsed time that remains correct across app backgrounding and delayed callbacks. A precision of 0.1 seconds for the visible countdown display. No process-termination persistence: if the app is killed, the running timer is lost. SwiftUI + Swift + Combine on the main thread. The same ideas apply to a stopwatch or interval timer; only the sign and…