feat(ui): add Open in CAD Converter to drawing context menu

Lets a single drawing be opened and edited in the CAD converter
directly from the drawing list, reusing the existing apply-back
logic from the Edit Drawings button (now shared via
EditDrawingsInConverter).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

OpenNest/Controls/DrawingListBox.cs

@@ -36,6 +36,13 @@ namespace OpenNest.Controls
                     SaveToLibraryRequested?.Invoke(this, drawing);
             };
             var saveToLibrarySeparator = new ToolStripSeparator();
+            var openInConverterItem = new ToolStripMenuItem("Open in CAD Converter...");
+            openInConverterItem.Click += (s, e) =>
+            {
+                if (SelectedItem is Drawing drawing)
+                    OpenInConverterRequested?.Invoke(this, drawing);
+            };
+            var openInConverterSeparator = new ToolStripSeparator();
             menu.ShowItemToolTips = true;
             menu.Opening += (s, e) =>
             {
@@ -49,9 +56,12 @@ namespace OpenNest.Controls
                 saveToLibraryItem.Visible = saveToLibrarySeparator.Visible = SaveToLibraryRequested != null;
                 saveToLibraryItem.Enabled = SaveToLibraryUnavailableReason == null;
                 saveToLibraryItem.ToolTipText = SaveToLibraryUnavailableReason ?? "";
+                openInConverterItem.Visible = openInConverterSeparator.Visible = OpenInConverterRequested != null;
             };
             menu.Items.Add(saveToLibraryItem);
             menu.Items.Add(saveToLibrarySeparator);
+            menu.Items.Add(openInConverterItem);
+            menu.Items.Add(openInConverterSeparator);
             menu.Items.Add(deleteItem);
             ContextMenuStrip = menu;
         }
@@ -64,6 +74,9 @@ namespace OpenNest.Controls
         /// <summary>Why Save to Drawing Library is disabled, shown as its tooltip; null enables it.</summary>
         public string SaveToLibraryUnavailableReason { get; set; }
 
+        /// <summary>Raised when Open in CAD Converter is chosen for the selected drawing.</summary>
+        public event EventHandler<Drawing> OpenInConverterRequested;
+
         /// <summary>
         /// Raised when the left button is pressed on a drawing's row.
         /// </summary>

OpenNest/Forms/EditNestForm.cs

@@ -440,6 +440,7 @@ namespace OpenNest.Forms
             drawingListBox1.Units = Nest.Units;
             drawingListBox1.DeleteRequested += drawingListBox1_DeleteRequested;
             drawingListBox1.SaveToLibraryRequested += drawingListBox1_SaveToLibraryRequested;
+            drawingListBox1.OpenInConverterRequested += drawingListBox1_OpenInConverterRequested;
             drawingListBox1.DrawingPickedUp += drawingListBox1_DrawingPickedUp;
             drawingListBox1.DrawingDropped += drawingListBox1_DrawingDropped;
             Activated += (_, _) => UpdateDrawingLibraryCommand();
@@ -1285,15 +1286,27 @@ namespace OpenNest.Forms
             if (Nest.Drawings.Count == 0)
                 return;
 
+            EditDrawingsInConverter(Nest.Drawings);
+        }
+
+        private void drawingListBox1_OpenInConverterRequested(object sender, Drawing drawing)
+        {
+            EditDrawingsInConverter(new[] { drawing });
+        }
+
+        private void EditDrawingsInConverter(IEnumerable<Drawing> drawings)
+        {
+            var editedDrawings = drawings.ToList();
+
             // Capture before loading the editor: its conversion can mutate programs in place.
             var snapshot = DrawingProgramSnapshot.Capture(
-                Nest.Drawings,
+                editedDrawings,
                 program => NestWriter.GetProgramText(program) + "\0" + NestWriter.GetSubProgramsText(program)
             );
             var converter = new CadConverterForm();
             // LoadDrawings can edit live programs even when the dialog is canceled.
             PlateView.InvalidateOverlapCheck();
-            converter.LoadDrawings(Nest.Drawings);
+            converter.LoadDrawings(editedDrawings);
 
             if (converter.ShowDialog() != DialogResult.OK)
                 return;
@@ -1302,7 +1315,7 @@ namespace OpenNest.Forms
             var newByName = newDrawings.ToDictionary(d => d.Name);
 
             // Update existing drawings in-place so parts keep their BaseDrawing references
-            foreach (var existing in Nest.Drawings.ToList())
+            foreach (var existing in editedDrawings)
             {
                 if (newByName.TryGetValue(existing.Name, out var updated))
                 {