CmdPal: Remove constrain that keeps the context menu flyout in the bounds of the window (#41133)

## Summary of the Pull Request

Added `ShouldConstrainToRootBounds="False"` to the Flyout element,
allowing it to extend beyond the bounds of its parent container. This
allows the menu to always open with top-left corner at the cursor
position as is common for the context menus.

This affects the menu only when opened as a context menu on the list
item (e.g. mouse right-click), not when opened from the Command Bar
(that opens same as before).

After screenshot:

<img width="834" height="589" alt="image"
src="https://github.com/user-attachments/assets/acb40e08-074e-4bae-afe7-87c6a73a6581"
/>


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## PR Checklist

- [x] Closes: #41131 
- [ ] **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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src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/CommandBar.xaml

@@ -47,7 +47,8 @@
             <Flyout
                 x:Name="ContextMenuFlyout"
                 FlyoutPresenterStyle="{StaticResource ContextMenuFlyoutStyle}"
-                Opened="ContextMenuFlyout_Opened">
+                Opened="ContextMenuFlyout_Opened"
+                ShouldConstrainToRootBounds="False">
                 <cpcontrols:ContextMenu x:Name="ContextControl" />
             </Flyout>