fix(cutting-ui): navigate selected source plate in planner

OpenNest.WinForms.Tests/Forms/CuttingInspectionPanelTests.cs

@@ -175,6 +175,7 @@ public class CuttingInspectionPanelTests
         Assert.False(Field<Button>(panel, "applyButton").Enabled);
         Assert.True(editor.PlateView.HasProposalDisplay);
         Field<Button>(panel, "nextButton").PerformClick();
+        Assert.Same(second, editor.PlateView.Plate); // Refusal shows the requested live plate, not the opening plate.
         Assert.False(editor.PlateView.HasProposalDisplay);
         Assert.Contains("no current preview", Field<Label>(panel, "previewLabel").Text);
         var grid = Field<DataGridView>(panel, "warningGrid");
@@ -188,6 +189,40 @@ public class CuttingInspectionPanelTests
         Assert.Same(original, editor.PlateView.Plate);
     });
 
+    [Fact]
+    public void NextAndPreviousShowTheSelectedReadyPlateNotTheOpeningPlate() => RunSta(() =>
+    {
+        using var editor = Editor();
+        var first = editor.Nest.Plates[0];
+        var second = editor.Nest.Plates[^1]; // Fill the managed sentinel.
+        second.Size = new OpenNest.Geometry.Size(100, 100);
+        second.Parts.Add(Square("other plate", 40));
+        editor.Show();
+        editor.PlateManager.LoadAt(0);
+        OpenAll(editor);
+        var panel = editor.CuttingInspection!;
+        PumpUntil(() => panel.Proposal != null && !panel.IsPlanning);
+        Assert.Equal(2, panel.Proposal.Plates.Count);
+        Assert.Same(first, editor.PlateView.Plate);
+        Assert.True(editor.PlateView.HasProposalDisplay);
+        Assert.Contains(editor.PlateView.DisplayPlate.Parts, part => part.BaseDrawing.Name == "near");
+
+        Field<Button>(panel, "nextButton").PerformClick();
+        Assert.Same(second, editor.PlateView.Plate);
+        Assert.True(editor.PlateView.HasProposalDisplay);
+        Assert.NotSame(second, editor.PlateView.DisplayPlate);
+        Assert.Single(editor.PlateView.DisplayPlate.Parts);
+        Assert.Equal("other plate", editor.PlateView.DisplayPlate.Parts[0].BaseDrawing.Name);
+        Assert.Contains("Plate 2", Field<Label>(panel, "previewLabel").Text);
+
+        Field<Button>(panel, "previousButton").PerformClick();
+        Assert.Same(first, editor.PlateView.Plate);
+        Assert.True(editor.PlateView.HasProposalDisplay);
+        Assert.Contains(editor.PlateView.DisplayPlate.Parts, part => part.BaseDrawing.Name == "near");
+        panel.RequestClose();
+        Assert.Same(first, editor.PlateView.Plate);
+    });
+
     [Fact]
     public void WarningAcceptanceResetsOnReplanAndSettingsOrderChange() => RunSta(() =>
     {

OpenNest/Forms/CuttingInspectionPanel.cs

@@ -436,7 +436,7 @@ internal sealed class CuttingInspectionPanel : UserControl
 
     private bool IsPreviewCurrent()
     {
-        if (!closed && !invalidated && ReferenceEquals(view.Plate, plate)
+        if (!closed && !invalidated && ReferenceEquals(view.Plate, plates[selectedPlate])
             && inspection.RefreshPreview(selectedPlate) != null)
             return true;
         invalidated = true;
@@ -454,6 +454,23 @@ internal sealed class CuttingInspectionPanel : UserControl
         selectedPlate = index;
         view.ClearProposalDisplay();
         view.ClearValidationFinding();
+        // Keep the authoritative editor plate on the selected live source even when
+        // no safe detached proposal can be rendered for that plate.
+        var sourceIndex = editor.Nest.Plates.IndexOf(plates[index]);
+        if (sourceIndex < 0)
+        {
+            ClearResult();
+            resultLabel.Text = "The selected plate changed after capture. Replan to continue.";
+            return;
+        }
+        if (!ReferenceEquals(view.Plate, plates[index]))
+            editor.PlateManager.LoadAt(sourceIndex);
+        if (!ReferenceEquals(view.Plate, plates[index]))
+        {
+            ClearResult();
+            resultLabel.Text = "The selected plate is no longer current. Replan to continue.";
+            return;
+        }
         if (plates[index].Parts.Count == 0)
         {
             preview = null;

docs/cutting-planner.md

@@ -399,12 +399,14 @@ panel is wired in the editor. Non-editor callers still use the shared analyzer.
 - The docked panel keeps the batch outcome and plate headings above a
   read-only, unsorted warning grid with Plate, source Part, With, and full finding text. Every
   overlap issue/pair and every planner finding has its own selectable row, including findings
-  hidden by the compact blocked-plate summary. Selecting a row switches to that plate's
-  detached preview and zooms to the affected part extent (or both parts for a pair), mapping
-  source positions to the proposed cutting order. This is not an exact contact marker: most
-  findings do not carry a geometric witness. If a plate cannot produce a current, supported
-  preview, no geometry is cloned or focused; the row still identifies its source part in the
-  editor. Replanning, cancellation and stale Apply clear old warning targets.
+  hidden by the compact blocked-plate summary. **Previous**/**Next** and warning selection
+  navigate the editor to that plate's live source sheet, then display its detached proposal
+  when available. Warning selection zooms to the affected part extent (or both parts for a
+  pair), mapping source positions to proposed cutting order. This is not an exact contact
+  marker: most findings do not carry a geometric witness. If a plate cannot produce a
+  current, supported proposal preview, its own live sheet remains visible; no unsupported
+  geometry is cloned or focused. Replanning, cancellation and stale Apply clear old warning
+  targets.
 - The summary lists every plate: ready plates with part counts and rapid travel, others
   with their status and findings. Unverified proposals retain every overlap and route
   warning in the selectable grid before the acceptance checkbox is used; they do