fix(ui): stop a grid's keyboard tooltip before the grid is disposed

Browsing nests in Database mode crashed with ObjectDisposedException on
DataGridView: selecting another nest drops the embedded version history,
and WinForms leaves its grid's keyboard-tooltip auto-pop timer running.
When the timer fired it hid the tooltip through the disposed grid.
GridStyle now hides that tooltip when a styled grid's window is destroyed,
which stops the timer for every grid in the app.

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

OpenNest.WinForms.Tests/Controls/GridStyleTests.cs

@@ -1,3 +1,4 @@
+using System.Reflection;
 using System.Windows.Forms;
 using OpenNest.Controls;
 
@@ -79,6 +80,33 @@ public class GridStyleTests
         Assert.Equal(column.Width, firstPaintWidth());
     });
 
+    [Fact]
+    public void DisposingAGridStopsItsShowingKeyboardToolTip() => ArchUnitsTests.RunSta(() =>
+    {
+        // WinForms leaves the keyboard tooltip's auto-pop timer running after the grid is
+        // disposed; when it fires it hides the tooltip through the disposed grid and throws.
+        const BindingFlags members = BindingFlags.Instance | BindingFlags.NonPublic;
+        using var form = new Form { Width = 600, Height = 300, ShowInTaskbar = false };
+        var grid = GridStyle.Apply(new DataGridView { Dock = DockStyle.Fill, AllowUserToAddRows = false });
+        grid.Columns.Add("Version", "Version");
+        grid.Rows.Add("2");
+        form.Controls.Add(grid);
+        form.Show();
+        Pump(grid);
+
+        // As when the keyboard moves to a cell in the embedded version history.
+        var toolTip = (ToolTip)typeof(DataGridView).GetProperty("KeyboardToolTip", members).GetValue(grid);
+        typeof(ToolTip).GetMethod("ShowKeyboardToolTip", members)
+            .Invoke(toolTip, new object[] { "2", grid.Rows[0].Cells[0], 3000 });
+        var timer = typeof(ToolTip).GetField("_timer", members);
+        Assert.NotNull(timer.GetValue(toolTip));
+
+        form.Controls.Remove(grid);
+        grid.Dispose();
+
+        Assert.Null(timer.GetValue(toolTip));
+    });
+
     private static Func<int> WidthAtFirstPaint(DataGridView grid, DataGridViewColumn column)
     {
         var width = -1;

OpenNest/Controls/GridStyle.cs

@@ -1,5 +1,6 @@
-using System;
+using System;
 using System.Drawing;
+using System.Reflection;
 using System.Windows.Forms;
 
 namespace OpenNest.Controls;
@@ -49,9 +50,28 @@ public static class GridStyle
         grid.RowHeadersDefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight;
         if (sizeColumns)
             SizeColumnsOnceToContent(grid);
+        grid.HandleDestroyed += HideToolTipsOnDestroy;
         return grid;
     }
 
+    private static readonly PropertyInfo KeyboardToolTipProperty = typeof(DataGridView).GetProperty(
+        "KeyboardToolTip", BindingFlags.Instance | BindingFlags.NonPublic);
+
+    /// <summary>
+    /// Hides the grid's keyboard tooltip while the grid's window still exists. WinForms does not
+    /// stop that tooltip's auto-pop timer when the grid is disposed, and the timer later hides the
+    /// tooltip through the disposed grid, which throws (as when the database browser drops its
+    /// embedded version history). Hiding it stops the timer. The tooltip is internal to WinForms,
+    /// so a runtime without it is left as it is.
+    /// </summary>
+    private static void HideToolTipsOnDestroy(object sender, EventArgs e)
+    {
+        var grid = (DataGridView)sender;
+        if (grid.RecreatingHandle || KeyboardToolTipProperty?.GetValue(grid) is not ToolTip toolTip)
+            return;
+        toolTip.Hide(grid);
+    }
+
     /// <summary>
     /// Widens each column to fit its header and its first rows, once, then leaves the widths
     /// to the user. Columns never stretch to fill the grid.