Stateful Submit Button

1/// A submit button that tells the whole story of an async action in one shape:2///3/// **idle** → tap → **loading** (the pill squeezes into a circle with a spinner)4/// → **success** (turns green, a checkmark draws itself, then it relaxes back)5/// or **failure** (turns red, shakes, and offers "Try again").6///7/// The action is `async throws`: return normally for success, throw for failure.8public struct StatefulSubmitButton: View {9    let title: String10    var systemImage: String?11    var successTitle: String12    var failureTitle: String13    var gradient: [Color]14    var height: CGFloat15    var resetDelay: Duration16    let action: () async throws -> Void17​18    private enum Phase: Equatable { case idle, loading, success, failure }19​20    @State private var phase: Phase = .idle21​22// ... (click "Show full code" to see more)