CmdPal: Setting Activation Shortcut now auto focuses on window & delivers dialog (#40968)

## Summary of the Pull Request
Screen readers now will focus on the activation shortcut windows and
read out the text

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## PR Checklist

- [x] Closes: #40967
- [x] **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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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments


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## Validation Steps Performed


https://github.com/user-attachments/assets/d72a9aea-28b8-49d1-b51f-7a7d2a8ff42f

src/modules/cmdpal/Microsoft.CmdPal.UI/Controls/ShortcutControl/ShortcutDialogContentControl.xaml

@@ -15,7 +15,7 @@
             <RowDefinition Height="Auto" />
         </Grid.RowDefinitions>
 
-        <TextBlock Grid.Row="0" />
+        <TextBlock Grid.Row="0" IsTabStop="True" />
 
         <ItemsControl
             x:Name="KeysControl"