Add interactive swipe-to-dismiss for iOS toasts

Toast cards now follow the finger upward and dismiss on either a
sufficient drag or a fast flick (via predicted-end translation). The
auto-dismiss timer pauses while the user is dragging and re-arms if
they release without dismissing.

Yattee/Services/ToastManager.swift

@@ -380,6 +380,20 @@ final class ToastManager {
         LoggingService.shared.info("Dismissed toast: \(id)", category: .general)
     }
 
+    /// Cancel the pending auto-dismiss timer for a toast (e.g. while user is interacting with it).
+    func pauseAutoDismiss(id: UUID) {
+        dismissTasks[id]?.cancel()
+        dismissTasks.removeValue(forKey: id)
+    }
+
+    /// Re-arm the auto-dismiss timer for a toast using its original delay.
+    func resumeAutoDismiss(id: UUID) {
+        guard let toast = activeToasts.first(where: { $0.id == id }) else { return }
+        guard !toast.isPersistent || toast.autoDismissDelay > 0 else { return }
+        dismissTasks[id]?.cancel()
+        scheduleAutoDismiss(for: toast)
+    }
+
     private func scheduleAutoDismiss(for toast: Toast) {
         let task = Task { [weak self] in
             try? await Task.sleep(for: .seconds(toast.autoDismissDelay))

Yattee/Views/Toast/ToastCardView.swift

@@ -12,8 +12,14 @@ struct ToastCardView: View {
     let toast: Toast
     let onDismiss: () -> Void
     let onAction: (() async -> Void)?
+    var onDragBegan: (() -> Void)? = nil
+    var onDragCancelled: (() -> Void)? = nil
 
     @State private var isAnimating = false
+    #if os(iOS)
+    @State private var dragOffset: CGFloat = 0
+    @State private var didNotifyDragBegan = false
+    #endif
 
     var body: some View {
         HStack(spacing: Self.iconSpacing) {
@@ -49,6 +55,13 @@ struct ToastCardView: View {
         .glassBackground(.regular, in: .capsule, fallback: .regularMaterial)
         .shadow(color: .black.opacity(0.15), radius: 10, y: 4)
         .scaleEffect(isAnimating ? 1 : 0.9)
+        #if os(iOS)
+        .compositingGroup()
+        .opacity(Double(1 - min(abs(min(dragOffset, 0)) / 120, 1)))
+        .offset(y: min(dragOffset, 0))
+        .contentShape(Capsule())
+        .simultaneousGesture(swipeGesture)
+        #endif
         .onAppear {
             withAnimation(.spring(response: 0.3, dampingFraction: 0.7)) {
                 isAnimating = true
@@ -56,6 +69,41 @@ struct ToastCardView: View {
         }
     }
 
+    #if os(iOS)
+    private var swipeGesture: some Gesture {
+        DragGesture()
+            .onChanged { value in
+                if !didNotifyDragBegan {
+                    didNotifyDragBegan = true
+                    onDragBegan?()
+                }
+                let h = value.translation.height
+                let target: CGFloat = h < 0 ? h : h * 0.2
+                var tx = Transaction()
+                tx.disablesAnimations = true
+                withTransaction(tx) {
+                    dragOffset = target
+                }
+            }
+            .onEnded { value in
+                didNotifyDragBegan = false
+                let translation = value.translation.height
+                let predicted = value.predictedEndTranslation.height
+                if translation < -60 || predicted < -200 {
+                    withAnimation(.easeOut(duration: 0.2)) {
+                        dragOffset = -200
+                    }
+                    onDismiss()
+                } else {
+                    withAnimation(.spring(response: 0.3, dampingFraction: 0.7)) {
+                        dragOffset = 0
+                    }
+                    onDragCancelled?()
+                }
+            }
+    }
+    #endif
+
     @ViewBuilder
     private var leadingIcon: some View {
         // Use fixed frame to prevent size changes when switching between spinner and icon

Yattee/Views/Toast/ToastOverlayView.swift

@@ -31,12 +31,15 @@ struct ToastOverlayView: View {
                     onDismiss: {
                         toastManager?.dismiss(id: toast.id)
                     },
-                    onAction: toast.action?.handler
+                    onAction: toast.action?.handler,
+                    onDragBegan: {
+                        toastManager?.pauseAutoDismiss(id: toast.id)
+                    },
+                    onDragCancelled: {
+                        toastManager?.resumeAutoDismiss(id: toast.id)
+                    }
                 )
                 .transition(.move(edge: .top).combined(with: .opacity))
-                #if !os(tvOS)
-                .gesture(swipeGesture(for: toast))
-                #endif
             }
         }
         .padding(.top, topPadding)
@@ -56,18 +59,6 @@ struct ToastOverlayView: View {
         return 60
         #endif
     }
-
-    #if !os(tvOS)
-    private func swipeGesture(for toast: Toast) -> some Gesture {
-        DragGesture()
-            .onEnded { value in
-                // Swipe up to dismiss
-                if value.translation.height < -50 {
-                    toastManager?.dismiss(id: toast.id)
-                }
-            }
-    }
-    #endif
 }
 
 // MARK: - View Extension