CmdPal: Prevent item template selectors from modifying containers (#45498)

## Summary of the Pull Request

This PR updates the item template selectors for ListView and GridView
and prevents them from modifying the container.
As a flyby, it introduces an enum for the list item type and centralizes
the logic that determines the type to the view model.

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## PR Checklist

- [x] Closes: #45496 
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issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **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
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

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## 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/ExtViews/ListPage.xaml

@@ -206,23 +206,30 @@
             x:Key="ListSectionContainerStyle"
             BasedOn="{StaticResource DefaultListViewItemStyle}"
             TargetType="ListViewItem">
+            <Setter Property="IsEnabled" Value="False" />
+            <Setter Property="AllowFocusWhenDisabled" Value="False" />
+            <Setter Property="AllowFocusOnInteraction" Value="False" />
             <Setter Property="IsHitTestVisible" Value="False" />
             <Setter Property="IsTabStop" Value="False" />
             <Setter Property="IsHoldingEnabled" Value="False" />
+            <Setter Property="AllowDrop" Value="False" />
             <Setter Property="Padding" Value="16,8,12,0" />
             <Setter Property="HorizontalContentAlignment" Value="Stretch" />
             <Setter Property="VerticalContentAlignment" Value="Bottom" />
             <Setter Property="MinHeight" Value="{StaticResource ListViewSectionMinHeight}" />
-            <Setter Property="AllowDrop" Value="False" />
         </Style>
 
         <Style
             x:Key="ListSeparatorContainerStyle"
             BasedOn="{StaticResource DefaultListViewItemStyle}"
             TargetType="ListViewItem">
+            <Setter Property="IsEnabled" Value="False" />
+            <Setter Property="AllowFocusWhenDisabled" Value="False" />
+            <Setter Property="AllowFocusOnInteraction" Value="False" />
             <Setter Property="IsHitTestVisible" Value="False" />
             <Setter Property="IsTabStop" Value="False" />
             <Setter Property="IsHoldingEnabled" Value="False" />
+            <Setter Property="AllowDrop" Value="False" />
             <Setter Property="Padding" Value="16,4,12,4" />
             <Setter Property="HorizontalContentAlignment" Value="Stretch" />
             <Setter Property="VerticalContentAlignment" Value="Center" />

src/modules/cmdpal/Microsoft.CmdPal.UI/ExtViews/ListPage.xaml.cs

@@ -1026,10 +1026,7 @@ public sealed partial class ListPage : Page,
         ItemView.SelectedIndex = newIndex;
     }
 
-    /// <summary>
-    ///  Code stealed from <see cref="Controls.ContextMenu.IsSeparator(object)"/>
-    /// </summary>
-    private bool IsSeparator(object? item) => item is ListItemViewModel li && li.IsSectionOrSeparator;
+    private bool IsSeparator(object? item) => item is ListItemViewModel li && !li.IsInteractive;
 
     private enum InputSource
     {