Context menu cleanup (#40584)

Addressing items in #40583

- [x] When navigating the context menu with the up/down keys, separators
should not be selectable.
- [x] [For context items with a super long title, we need to trim those
with an ellipsis. Ideally, we'd show a tooltip for just those
items.](https://github.com/microsoft/PowerToys/issues/40313)
- [x] [Context menu search bar text size doesn't update after changing
system text size](https://github.com/microsoft/PowerToys/issues/39648)
- [x] Weird "kick out" on first context menu item
- [x] [Primary button doesn't work if the command has more items (fix
regression)](https://github.com/microsoft/PowerToys/issues/40624)

Example of long context menu item titles with tooltips: (@niels9001,
look okay?)


https://github.com/user-attachments/assets/fc0a4034-9c22-48ee-a3f0-44fcc2f294a6

closes #40624

src/modules/cmdpal/Microsoft.CmdPal.Core.ViewModels/ContextMenuViewModel.cs

@@ -22,15 +22,8 @@ public partial class ContextMenuViewModel : ObservableObject,
         get => field;
         set
         {
-            if (field != null)
-            {
-                field.PropertyChanged -= SelectedItemPropertyChanged;
-            }
-
             field = value;
-            SetSelectedItem(value);
-
-            OnPropertyChanged(nameof(SelectedItem));
+            UpdateContextItems();
         }
     }
 
@@ -68,33 +61,6 @@ public partial class ContextMenuViewModel : ObservableObject,
         OnPropertyChanged(nameof(FilterOnTop));
     }
 
-    private void SetSelectedItem(ICommandBarContext? value)
-    {
-        if (value != null)
-        {
-            value.PropertyChanged += SelectedItemPropertyChanged;
-        }
-        else
-        {
-            if (SelectedItem != null)
-            {
-                SelectedItem.PropertyChanged -= SelectedItemPropertyChanged;
-            }
-        }
-
-        UpdateContextItems();
-    }
-
-    private void SelectedItemPropertyChanged(object? sender, System.ComponentModel.PropertyChangedEventArgs e)
-    {
-        switch (e.PropertyName)
-        {
-            case nameof(SelectedItem.HasMoreCommands):
-                UpdateContextItems();
-                break;
-        }
-    }
-
     public void UpdateContextItems()
     {
         if (SelectedItem != null)