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/ext/SamplePagesExtension/Pages/SampleListPage.cs

@@ -99,7 +99,7 @@ internal sealed partial class SampleListPage : ListPage
                             new CommandContextItem(
                                 new ToastCommand("Nested B invoked") { Name = "Do it", Icon = new IconInfo("B") })
                             {
-                                Title = "Nested B...",
+                                Title = "Nested B with a really, really long title that should be trimmed",
                                 RequestedShortcut = KeyChordHelpers.FromModifiers(ctrl: true, vkey: VirtualKey.B),
                                 MoreCommands = [
                                     new CommandContextItem(