adds quick question UI for mac catalyst target

ios/Packages/Sybil/Sources/Sybil/SybilMacWindowCommands.swift

@@ -0,0 +1,37 @@
+#if targetEnvironment(macCatalyst)
+import Combine
+
+// Scene lifetime is independent of focused commands: a connected window may
+// still be authenticating, inactive, or minimized. The native Quick Question
+// panel is not a workspace scene and does not count as an open window here.
+@MainActor
+public final class SybilMacWindowCommands: ObservableObject {
+    public static let shared = SybilMacWindowCommands()
+
+    @Published private var connectedWindowIDs: Set<String> = []
+
+    init() {}
+
+    var hasOpenWindows: Bool { !connectedWindowIDs.isEmpty }
+
+    public func windowConnected(sessionID: String) {
+        connectedWindowIDs.insert(sessionID)
+    }
+
+    public func windowDisconnected(sessionID: String) {
+        connectedWindowIDs.remove(sessionID)
+    }
+
+    func canStartNewChat(hasFocusedActions: Bool) -> Bool {
+        !hasOpenWindows || hasFocusedActions
+    }
+
+    func newChatOrWindow(newChat: (() -> Void)?, openWindow: () -> Void) {
+        if hasOpenWindows {
+            newChat?()
+        } else {
+            openWindow()
+        }
+    }
+}
+#endif