fix: pass through exception message directly instead of generic wrapper

- BuildFromFaceNormal already provides specific error like '面法向与光轴平行'
- Catch now shows raw ex.Message instead of prefixing with generic text

src/UI/WPF/ViewModels/PathEditingViewModel.cs

@@ -2500,11 +2500,11 @@ namespace NavisworksTransport.UI.WPF.ViewModels
             {
                 LogManager.Error($"[直线装配] 端面分析失败: {ex.Message}", ex);
                 DialogHelper.ShowStatusAndDialog(
-                    $"端面分析失败: {ex.Message}",
+                    ex.Message,
                     "取端面失败",
-                    $"端面分析失败: {ex.Message}\n请确保点击的是终点箱体的平整端面。",
+                    ex.Message,
                     UpdateMainStatus,
-                    System.Windows.MessageBoxImage.Error,
+                    System.Windows.MessageBoxImage.Warning,
                     5000);
             }
             finally
@@ -2630,11 +2630,11 @@ namespace NavisworksTransport.UI.WPF.ViewModels
                 LogManager.Error($"[直线装配] 安装面分析失败: {ex.Message}", ex);
                 CleanupAssemblyInstallationSelection();
                 DialogHelper.ShowStatusAndDialog(
-                    $"安装面分析失败: {ex.Message}",
+                    ex.Message,
                     "选安装面失败",
-                    $"安装面分析失败: {ex.Message}\n请确保点击的是终点箱体表面的平整区域。",
+                    ex.Message,
                     UpdateMainStatus,
-                    System.Windows.MessageBoxImage.Error,
+                    System.Windows.MessageBoxImage.Warning,
                     5000);
             }
         }