fix(AppDelegate): 关闭窗口时保持应用运行

作为菜单栏应用，点击窗口关闭按钮不应退出程序，否则轮询与通知会停止。
applicationShouldTerminateAfterLastWindowClosed 返回 false；退出仅通过
弹层 Quit 按钮或 Cmd+Q。

Sources/AppDelegate.swift

@@ -36,6 +36,15 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
         }
     }
 
+    // MARK: - NSApplicationDelegate
+
+    /// Bugger is a menu-bar app: closing a window must not quit it, otherwise
+    /// polling and notifications would stop. Quit only via the Quit button
+    /// or Cmd+Q.
+    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+        false
+    }
+
     private func setupStatusItem() {
         statusItem = NSStatusBar.system.statusItem(withLength: NSStatusItem.variableLength)
         if let button = statusItem.button {