[feat] add Linux X11 resolution controls with disconnect restore

docs/USER_GUIDE.md

@@ -139,6 +139,8 @@ macOS 保留一个 CrossDesk Dock 应用图标，主窗口与远程控制窗口
 
 连接成功后，点击工具栏中的 **画面设置**（滑杆图标），直接选择低 / 中 / 高画质、**30 / 60 fps**，以及帧率优先 / 画质优先 / 平衡。选项会发送给当前被控端，无需断开重连；实际画面效果取决于网络、设备与编码器能力。旧版被控端不支持时，菜单会提示并禁用选项。
 
+被控端为 Windows、macOS 或 Linux X11 时，还可在 **画面设置 → 分辨率** 中选择当前显示器支持的桌面分辨率。调整无需重连，最后一个控制端断开后会恢复连接期间首次调整前的显示模式。Linux 需要使用 X11 采集及支持 RandR 的显示服务器；Wayland、XWayland 和使用自定义缩放或平移的显示配置暂不支持。可选分辨率由显示器或虚拟显示服务器提供，仅提供一个模式的虚拟屏不会额外生成模式。
+
 <p align="center">
   <img src="images/desktop-stream-video-settings-zh.png" width="800" alt="当前远程会话的画面设置菜单：画面质量、采集帧率与画面偏好；背景为公开页面演示图" />
 </p>

docs/USER_GUIDE_EN.md

@@ -139,6 +139,8 @@ Network statistics in both ordinary sessions and DeskHub show the video codecs a
 
 After connecting, open **Video settings** (the sliders icon) in the toolbar. Choose low / medium / high quality, **30 / 60 fps**, and frame-rate priority / quality priority / balanced adaptation. Changes are sent to the current host without reconnecting; actual results depend on the network, device, and encoder. For older hosts that do not support live video settings, the menu explains the limitation and disables the options.
 
+For Windows, macOS, and Linux X11 hosts, **Video settings → Resolution** also lists supported desktop resolutions for the selected monitor. Changes take effect without reconnecting; when the last controller disconnects, the display mode from before the first change is restored. Linux requires X11 capture and a RandR-capable display server. Wayland, XWayland, and custom scaling or panning configurations are not supported. Choices come from the monitor or virtual display server; no additional modes are created for virtual screens that expose only one mode.
+
 <p align="center">
   <img src="images/desktop-stream-video-settings-en.png" width="800" alt="Current session video menu with quality, capture frame rate, and video preference; the background is a public page used for demonstration" />
 </p>