CmdPal: Allow list item context menu (#45086)

## Summary of the Pull Request

This PR enables pointer-invoked context menus for list items when the
list contains at least one item, including the primary item.

The command bar "More" button or Ctrl+K hotkey remain unaffected - the
menu is not accessible through those.

<img width="453" height="210" alt="image"
src="https://github.com/user-attachments/assets/af0f38e3-e1e7-4968-9e2d-6d9293785ab1"
/>


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## PR Checklist

- [x] Closes: #45083
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
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

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/CommandBar.xaml.cs

@@ -44,13 +44,14 @@ public sealed partial class CommandBar : UserControl,
 
     public void Receive(OpenContextMenuMessage message)
     {
-        if (!ViewModel.ShouldShowContextMenu)
-        {
-            return;
-        }
-
         if (message.Element is null)
         {
+            // This is invoked from the "More" button on the command bar
+            if (!ViewModel.ShouldShowContextMenu)
+            {
+                return;
+            }
+
             _ = DispatcherQueue.TryEnqueue(
                 () =>
                 {
@@ -65,6 +66,7 @@ public sealed partial class CommandBar : UserControl,
         }
         else
         {
+            // This is invoked from a specific element
             _ = DispatcherQueue.TryEnqueue(
             () =>
             {