feat: disable SolidWorks user input during export

Sets CommandInProgress to block user interaction with SolidWorks
while the DXF export is running, preventing accidental interference.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ExportDXF/Forms/MainForm.cs

@@ -341,6 +341,8 @@ namespace ExportDXF.Forms
                 LogMessage($"Started at {DateTime.Now:t}");
                 LogMessage($"Exporting to: {_fileExportService.OutputFolder}");
 
+                _solidWorksService.SetCommandInProgress(true);
+
                 await Task.Run(() => _exportService.Export(exportContext), token);
 
                 LogMessage("Done.");
@@ -356,6 +358,7 @@ namespace ExportDXF.Forms
             }
             finally
             {
+                _solidWorksService.SetCommandInProgress(false);
                 UpdateUIForExportComplete();
                 _cancellationTokenSource?.Dispose();
                 _cancellationTokenSource = null;

ExportDXF/Services/SolidWorksService.cs

@@ -88,6 +88,13 @@ namespace ExportDXF.Services
         /// <param name="enable">True to enable user control, false to disable.</param>
         void EnableUserControl(bool enable);
 
+        /// <summary>
+        /// Sets whether a command is in progress. When true, user input to
+        /// SolidWorks is disabled and interactive dialogs are suppressed.
+        /// </summary>
+        /// <param name="inProgress">True to block user input, false to re-enable.</param>
+        void SetCommandInProgress(bool inProgress);
+
         /// <summary>
         /// Gets the SolidWorks application instance.
         /// </summary>
@@ -188,6 +195,15 @@ namespace ExportDXF.Services
             }
         }
 
+        /// <inheritdoc />
+        public void SetCommandInProgress(bool inProgress)
+        {
+            if (_sldWorks != null)
+            {
+                _sldWorks.CommandInProgress = inProgress;
+            }
+        }
+
         /// <summary>
         /// Gets the native SolidWorks application instance.
         /// Use this when you need direct access to the SolidWorks API.