CmdPal: Fix dock popup XamlRoot handling on DockControl (#46305)

## Summary of the Pull Request

This PR handles situations when app can crash because a popup control is
being touched before XamlRoot is set.

- Registers message handlers in DockControl only while controls are
loaded.
- Guards the edit-mode TeachingTip until the dock is rooted.
- Sets XamlRoot for dock flyouts and tooltips before showing.
- Ensures that tooltips in DockItemControl are set only after XamlRoot
is explicitly set.
- Unregisteres messages and CenterItems_CollectionChanged when unloaded.

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## PR Checklist

- [x] Closes: #46228
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issues) -->
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- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
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- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
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and link it here: #xxx

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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

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wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/Dock/DockControl.xaml.cs

@@ -67,15 +67,52 @@ public sealed partial class DockControl : UserControl, IRecipient<CloseContextMe
     {
         _viewModel = viewModel;
         InitializeComponent();
-        WeakReferenceMessenger.Default.Register<CloseContextMenuMessage>(this);
-        WeakReferenceMessenger.Default.Register<EnterDockEditModeMessage>(this);
-
-        ViewModel.CenterItems.CollectionChanged += CenterItems_CollectionChanged;
+        Loaded += DockControl_Loaded;
+        Unloaded += DockControl_Unloaded;
 
         // Start with edit mode disabled - normal click behavior
         UpdateEditMode(false);
     }
 
+    private void DockControl_Loaded(object sender, RoutedEventArgs e)
+    {
+        WeakReferenceMessenger.Default.UnregisterAll(this);
+        WeakReferenceMessenger.Default.Register<CloseContextMenuMessage>(this);
+        WeakReferenceMessenger.Default.Register<EnterDockEditModeMessage>(this);
+
+        ViewModel.CenterItems.CollectionChanged -= CenterItems_CollectionChanged;
+        ViewModel.CenterItems.CollectionChanged += CenterItems_CollectionChanged;
+
+        UpdateEditModeTeachingTip();
+    }
+
+    private void DockControl_Unloaded(object sender, RoutedEventArgs e)
+    {
+        WeakReferenceMessenger.Default.UnregisterAll(this);
+
+        ViewModel.CenterItems.CollectionChanged -= CenterItems_CollectionChanged;
+
+        if (EditButtonsTeachingTip.IsOpen)
+        {
+            EditButtonsTeachingTip.IsOpen = false;
+        }
+
+        if (ContextMenuFlyout.IsOpen)
+        {
+            ContextMenuFlyout.Hide();
+        }
+
+        if (AddBandFlyout.IsOpen)
+        {
+            AddBandFlyout.Hide();
+        }
+
+        if (EditModeContextMenu.IsOpen)
+        {
+            EditModeContextMenu.Hide();
+        }
+    }
+
     private void CenterItems_CollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
     {
         UpdateCenterVisibility();
@@ -125,7 +162,38 @@ public sealed partial class DockControl : UserControl, IRecipient<CloseContextMe
             };
         }
 
-        EditButtonsTeachingTip.IsOpen = isEditMode;
+        UpdateEditModeTeachingTip();
+    }
+
+    private void UpdateEditModeTeachingTip()
+    {
+        if (XamlRoot is null || ContentGrid.XamlRoot is null || EditButtonsTeachingTip.Parent is null)
+        {
+            return;
+        }
+
+        if (!IsEditMode)
+        {
+            if (EditButtonsTeachingTip.IsOpen)
+            {
+                EditButtonsTeachingTip.IsOpen = false;
+            }
+
+            return;
+        }
+
+        if (!EditButtonsTeachingTip.IsOpen)
+        {
+            EditButtonsTeachingTip.IsOpen = true;
+        }
+    }
+
+    private static void PreparePopupForShow(FlyoutBase popup, FrameworkElement placementTarget)
+    {
+        if (placementTarget.XamlRoot is not null && popup.XamlRoot != placementTarget.XamlRoot)
+        {
+            popup.XamlRoot = placementTarget.XamlRoot;
+        }
     }
 
     internal void EnterEditMode()
@@ -214,6 +282,7 @@ public sealed partial class DockControl : UserControl, IRecipient<CloseContextMe
                     ShowTitlesMenuItem.IsChecked = _editModeContextBand.ShowTitles;
                     ShowSubtitlesMenuItem.IsChecked = _editModeContextBand.ShowSubtitles;
 
+                    PreparePopupForShow(EditModeContextMenu, dockItem);
                     EditModeContextMenu.ShowAt(
                         dockItem,
                         new FlyoutShowOptions()
@@ -232,6 +301,7 @@ public sealed partial class DockControl : UserControl, IRecipient<CloseContextMe
             {
                 ContextControl.ViewModel.SelectedItem = item;
                 ContextControl.ShowFilterBox = true;
+                PreparePopupForShow(ContextMenuFlyout, dockItem);
                 ContextMenuFlyout.ShowAt(
                     dockItem,
                     new FlyoutShowOptions()
@@ -320,6 +390,7 @@ public sealed partial class DockControl : UserControl, IRecipient<CloseContextMe
         {
             ContextControl.ViewModel.SelectedItem = item;
             ContextControl.ShowFilterBox = false;
+            PreparePopupForShow(ContextMenuFlyout, RootGrid);
             ContextMenuFlyout.ShowAt(
             this.RootGrid,
             new FlyoutShowOptions()
@@ -516,6 +587,7 @@ public sealed partial class DockControl : UserControl, IRecipient<CloseContextMe
             AddBandListView.Visibility = hasAvailableBands ? Visibility.Visible : Visibility.Collapsed;
 
             // Show the flyout
+            PreparePopupForShow(AddBandFlyout, button);
             AddBandFlyout.ShowAt(button);
         }
     }

src/modules/cmdpal/Microsoft.CmdPal.UI/Dock/DockItemControl.xaml.cs

@@ -35,10 +35,7 @@ public sealed partial class DockItemControl : Control
     {
         if (d is DockItemControl control)
         {
-            // Collapse the tooltip when the string is null or empty so an
-            // empty tooltip bubble doesn't appear on hover.
-            var text = e.NewValue as string;
-            ToolTipService.SetToolTip(control, string.IsNullOrEmpty(text) ? null : text);
+            control.UpdateToolTip();
         }
     }
 
@@ -91,6 +88,7 @@ public sealed partial class DockItemControl : Control
 
     private FrameworkElement? _iconPresenter;
     private DockControl? _parentDock;
+    private ToolTip? _toolTip;
     private long _dockSideCallbackToken = -1;
 
     private static void OnTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
@@ -184,9 +182,33 @@ public sealed partial class DockItemControl : Control
     {
         UpdateTextVisibility();
         UpdateIconVisibility();
+        UpdateToolTip();
         UpdateAlignment();
     }
 
+    private void UpdateToolTip()
+    {
+        var text = ToolTip;
+        if (string.IsNullOrEmpty(text))
+        {
+            ToolTipService.SetToolTip(this, null);
+            _toolTip = null;
+            return;
+        }
+
+        // Wait until the control is connected to a XamlRoot before creating
+        // the tooltip popup; dock items are materialized very early in startup.
+        if (XamlRoot is null)
+        {
+            return;
+        }
+
+        _toolTip ??= new ToolTip();
+        _toolTip.Content = text;
+        _toolTip.XamlRoot = XamlRoot;
+        ToolTipService.SetToolTip(this, _toolTip);
+    }
+
     protected override void OnApplyTemplate()
     {
         base.OnApplyTemplate();
@@ -232,6 +254,8 @@ public sealed partial class DockItemControl : Control
                 DockControl.DockSideProperty,
                 OnParentDockSideChanged);
         }
+
+        UpdateToolTip();
     }
 
     private void DockItemControl_ActualThemeChanged(FrameworkElement sender, object args)
@@ -250,6 +274,9 @@ public sealed partial class DockItemControl : Control
             _dockSideCallbackToken = -1;
             _parentDock = null;
         }
+
+        ToolTipService.SetToolTip(this, null);
+        _toolTip = null;
     }
 
     private void OnParentDockSideChanged(DependencyObject sender, DependencyProperty dp)