changed.项目结构优化

platform/LanMountainDesktop.Platform/IMainWindowDesktopLayerService.cs

@@ -0,0 +1,30 @@
+using Avalonia.Controls;
+
+namespace LanMountainDesktop.Platform.Abstractions;
+
+/// <summary>
+/// 主窗口桌面层服务接口。将主窗口嵌入系统桌面图标层（仅 Windows 支持）。
+/// </summary>
+public interface IMainWindowDesktopLayerService
+{
+    bool IsSupported { get; }
+    void EnableOrRefresh(Window window);
+    void Disable(Window window);
+}
+
+/// <summary>
+/// 无操作实现。用于不支持桌面层嵌入的平台（Linux/macOS/移动端）。
+/// </summary>
+public sealed class NullMainWindowDesktopLayerService : IMainWindowDesktopLayerService
+{
+    public bool IsSupported => false;
+
+    public void EnableOrRefresh(Window window)
+    {
+        PlatformLog.Info("MainWindowDesktopLayer", "Desktop layer requested on an unsupported platform.");
+    }
+
+    public void Disable(Window window)
+    {
+    }
+}