Actor Isolation Fixer

Instructions

Fix actor isolation errors systematically:

1. Error: "main actor-isolated property X cannot be accessed from nonisolated"

   • In deinit: Mark property as nonisolated(unsafe) private var
   • In closure: Add @MainActor to Task or use await MainActor.run { }
   • In method: Mark method @MainActor or nonisolated

2. Common Leavn patterns:

   // Timer in @MainActor class deinit
   nonisolated(unsafe) private var timer: Timer?
   
   deinit {
       timer?.invalidate() // Safe - Timer.invalidate() is thread-safe
   }