CmdPal: Add URI protocol command to reload extension (#41445)

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fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request

This PR introduces a new way to reload extensions externally and makes
the feature configurable in the settings UI.

- Adds a new URI protocol command `x-cmdpal://reload` → triggers an
extension reload
- Introduces a new "For Developers" section on the General settings page
- Includes an option to enable/disable the external reload feature
- **Note:** This change depends on the fix in #41344 to work correctly. 

Pictures? Pictures!

<img width="2312" height="1334" alt="image"
src="https://github.com/user-attachments/assets/6457ef5b-e75e-4118-86b7-7e20505527a3"
/>

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## PR Checklist

- [x] Closes: #40542 
- [ ] **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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## Validation Steps Performed

src/modules/cmdpal/Microsoft.CmdPal.UI/MainWindow.xaml.cs

@@ -521,6 +521,21 @@ public sealed partial class MainWindow : WindowEx,
                             WeakReferenceMessenger.Default.Send<OpenSettingsMessage>(new());
                             return;
                         }
+                        else if (uri.StartsWith("x-cmdpal://reload", StringComparison.OrdinalIgnoreCase))
+                        {
+                            var settings = App.Current.Services.GetService<SettingsModel>();
+                            if (settings?.AllowExternalReload == true)
+                            {
+                                Logger.LogInfo("External Reload triggered");
+                                WeakReferenceMessenger.Default.Send<ReloadCommandsMessage>(new());
+                            }
+                            else
+                            {
+                                Logger.LogInfo("External Reload is disabled");
+                            }
+
+                            return;
+                        }
                     }
                 }
             }