improve:墨迹保存

Ink Canvas/MainWindow_cs/MW_Save&OpenStrokes.cs

@@ -54,18 +54,23 @@ namespace Ink_Canvas {
                         }
                     }
                     catch (Exception fallbackEx) {
-                        // 如果默认路径失败，切换到 C 盘根目录
+                        // 如果文档路径保存失败，尝试用户目录
-                        var cRootPath = @"C:\墨迹备份\" + Path.GetFileName(docPath);
+                        string userDocPath = Path.Combine(
+                            Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
+                            "Documents",
+                            "墨迹备份",
+                            Path.GetFileName(docPath)
+                        );
+
                         try {
-                            Directory.CreateDirectory(Path.GetDirectoryName(cRootPath));
+                            Directory.CreateDirectory(Path.GetDirectoryName(userDocPath));
-                            using (FileStream fs = new FileStream(cRootPath, FileMode.Create)) {
+                            using (FileStream fs = new FileStream(userDocPath, FileMode.Create)) {
                                 inkCanvas.Strokes.Save(fs);
-                                savePathWithName = cRootPath; // 使用 C 盘路径替代
+                                savePathWithName = userDocPath;
-                                ShowNotification("墨迹保存至 C 盘: " + cRootPath); // 提示用户变更路径
                             }
                         }
-                        catch (Exception cRootEx) {
+                        catch (Exception userFallbackEx) {
-                            ShowNotification($"墨迹保存失败: {cRootEx.Message}");
+                            ShowNotification($"墨迹保存失败: {userFallbackEx.Message}");
                             return;
                         }
                     }