feat(simulator): lock the nest to viewing while the cut simulator is open

The simulator reuses Plan Cutting's inspection lock: the canvas pans and
zooms and plates can be stepped through, but selection, part edits,
menus, toolbars, lists and Undo/Redo are disabled until it closes.
Escape or closing the nest closes the simulator first.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest/Forms/CutSimulatorForm.cs

@@ -10,6 +10,8 @@ namespace OpenNest.Forms
     /// <summary>
     /// Playback controls for a <see cref="CutSimulationOverlay"/> on a nest's plate view. Follows
     /// the current plate and rebuilds the timeline when parts are added, removed or resequenced.
+    /// While it is open the nest is view-only, as in Plan Cutting: the canvas pans and zooms and
+    /// plates can be stepped through, but nothing that edits is enabled.
     /// </summary>
     public sealed class CutSimulatorForm : Form
     {
@@ -26,6 +28,7 @@ namespace OpenNest.Forms
         private readonly NumericUpDown feedBox, holeFeedBox, rapidBox, pierceBox;
         private readonly CheckBox skipEtchBox;
         private readonly CutTimeMachineBox machineBox;
+        private readonly ValidationInspectionScope scope;
         private Plate plate;
         private bool updatingTrack;
         private bool rebuildQueued;
@@ -184,6 +187,9 @@ namespace OpenNest.Forms
             nestForm.FormClosed += NestForm_FormClosed;
             AttachPlate(nestForm.PlateView.Plate);
             Rebuild();
+
+            scope = new ValidationInspectionScope(nestForm, Close, nestForm.PlateNavigation);
+            nestForm.PlateView.InspectionCloseRequested = Close;
         }
 
         private static NumericUpDown NewNumber(decimal value, decimal min, decimal max, int decimals, string suffix) =>
@@ -447,9 +453,16 @@ namespace OpenNest.Forms
             nestForm.FormClosed -= NestForm_FormClosed;
             AttachPlate(null);
             if (!nestForm.PlateView.IsDisposed)
+            {
                 overlay.Clear();
+                nestForm.PlateView.InspectionCloseRequested = null;
+            }
 
             base.OnFormClosed(e);
+
+            // Unlock after the editor has forgotten this form, then finish a close it held up.
+            scope.Dispose();
+            scope.ResumeHostClose();
         }
 
         // Playback rewrites the status every frame; a plain label erases before it redraws, so it flashes.

OpenNest/Forms/CuttingInspectionPanel.cs

@@ -401,7 +401,7 @@ internal sealed class CuttingInspectionPanel : UserControl
 
     internal void Open()
     {
-        scope = new ValidationInspectionScope(editor, this, editor.SidePanelHeader, RequestClose);
+        scope = new ValidationInspectionScope(editor, RequestClose, this, editor.SidePanelHeader);
         view.InspectionCloseRequested = RequestClose;
         view.OverlapDisplay = OverlapDisplayMode.Off;
         view.ClearValidationFinding();

OpenNest/Forms/EditNestForm.Designer.cs

@@ -16,6 +16,9 @@
             // A planning worker owns a captured inspection until its owner-thread join.
             if (disposing && DeferCuttingDisposal())
                 return;
+            // The simulator's lock disables the main window until it closes.
+            if (disposing)
+                cutSimulatorForm?.Close();
             if (disposing && (components != null))
             {
                 components.Dispose();

OpenNest/Forms/EditNestForm.Undo.cs

@@ -58,7 +58,7 @@ namespace OpenNest.Forms
 
         public bool CanRedo => History.CanRedo && CanRestore;
 
-        private bool CanRestore => !IsChangeInProgress && CuttingInspection == null;
+        private bool CanRestore => !IsChangeInProgress && !IsInspecting;
 
         public void Undo()
         {

OpenNest/Forms/EditNestForm.cs

@@ -176,6 +176,7 @@ namespace OpenNest.Forms
             plateButtons.Controls.AddRange(
                 new Control[] { btnFirstPlate, btnPreviousPlate, btnNextPlate, btnLastPlate });
             ZoomControls = [zoomOutButton, zoomInButton, zoomToFitButton];
+            PlateNavigation = plateButtons;
 
             zoomOutButton.Location = new Point(btnSize.Width * 4 + 8, 0);
             zoomInButton.Location = new Point(btnSize.Width * 5 + 8, 0);
@@ -281,7 +282,20 @@ namespace OpenNest.Forms
 
         internal Control SidePanelHeader { get; private set; }
         internal Control[] ZoomControls { get; private set; }
+        internal Control PlateNavigation { get; private set; }
         internal CuttingInspectionPanel CuttingInspection { get; private set; }
+
+        /// <summary>True while Plan Cutting or the Cut Simulator holds the nest view-only.</summary>
+        internal bool IsInspecting => CuttingInspection != null || cutSimulatorForm != null;
+
+        internal void EndInspection()
+        {
+            if (CuttingInspection != null)
+                CuttingInspection.RequestClose();
+            else
+                cutSimulatorForm?.Close();
+        }
+
         private bool disposeAfterCuttingInspection;
         private bool closeAfterCuttingInspection;
         internal bool DeferCuttingDisposal()
@@ -1118,7 +1132,10 @@ namespace OpenNest.Forms
                 cutSimulatorForm.Activate();
                 return;
             }
+            if (CuttingInspection != null)
+                return;
 
+            PlateView.EndAction();
             cutSimulatorForm = new CutSimulatorForm(this);
             cutSimulatorForm.FormClosed += (_, _) => cutSimulatorForm = null;
             var owner = MdiParent ?? (Form)this;

OpenNest/Forms/MainForm.cs

@@ -75,13 +75,12 @@ namespace OpenNest.Forms
 
         protected override bool ProcessCmdKey(ref Message msg, Keys keyData)
         {
-            var inspection = MdiChildren.OfType<EditNestForm>()
-                .Select(form => form.CuttingInspection).FirstOrDefault(panel => panel != null);
-            if (inspection != null)
+            var inspected = MdiChildren.OfType<EditNestForm>().FirstOrDefault(form => form.IsInspecting);
+            if (inspected != null)
             {
                 if (keyData == Keys.Escape)
                 {
-                    inspection.RequestClose();
+                    inspected.EndInspection();
                     return true;
                 }
                 // Standard inspection navigation reaches the canvas/panel; menu shortcuts cannot mutate.

OpenNest/Forms/ValidationInspectionScope.cs

@@ -6,7 +6,11 @@ using OpenNest.Controls;
 
 namespace OpenNest.Forms;
 
-/// <summary>Keep live validation inputs stable while allowing navigation of the main canvas.</summary>
+/// <summary>
+/// Keep live validation inputs stable while allowing navigation of the main canvas. Locks the
+/// canvas to viewing and disables every other control of the main window except
+/// <c>keepLive</c> and the zoom buttons.
+/// </summary>
 internal sealed class ValidationInspectionScope : IDisposable
 {
     private readonly List<(Control Control, bool Enabled)> controls = new();
@@ -18,11 +22,11 @@ internal sealed class ValidationInspectionScope : IDisposable
     private Form closingHost;
     private readonly bool previousInspection;
 
-    public ValidationInspectionScope(EditNestForm editor, Control inspector, Control header, Action close)
+    public ValidationInspectionScope(EditNestForm editor, Action close, params Control[] keepLive)
     {
         view = editor.PlateView;
         // The header zoom buttons only change the viewport, like the canvas wheel.
-        live = new[] { view, inspector, header }.Concat(editor.ZoomControls).Where(control => control != null).ToArray();
+        live = keepLive.Prepend(view).Concat(editor.ZoomControls).Where(control => control != null).ToArray();
         this.close = close;
         previousInspection = view.InspectionOnly;
         view.InspectionOnly = true;