Application notification manager throws on a partial trust application

### Describe the bug

The [AppNotificationManager](https://learn.microsoft.com/en-us/windows/windows-app-sdk/api/winrt/microsoft.windows.appnotifications.appnotificationmanager?view=windows-app-sdk-2.0) fails to work on a partial trust application WinUI 3 project despite [AppNotificationManager.IsSupported](https://learn.microsoft.com/en-us/windows/windows-app-sdk/api/winrt/microsoft.windows.appnotifications.appnotificationmanager.issupported?view=windows-app-sdk-2.0) returning true.

Calling [AppNotificationManager.Register](https://learn.microsoft.com/en-us/windows/windows-app-sdk/api/winrt/microsoft.windows.appnotifications.appnotificationmanager.register?view=windows-app-sdk-2.0) throws `System.Runtime.InteropServices.COMException: 'Unspecified error No COM servers are registered for this app'`.

Calling [AppNotificationManager.Show](https://learn.microsoft.com/en-us/windows/windows-app-sdk/api/winrt/microsoft.windows.appnotifications.appnotificationmanager.show?view=windows-app-sdk-2.0) throws `System.Runtime.InteropServices.COMException: 'The request is not supported. The request is not supported.'`.

### Steps to reproduce the bug

1. Create a MSIX packaged WinUI 3 project.
2. Change `EntryPoint`'s value to `windows.partialTrustApplication`.
3. Comment out the `runFullTrust` & `systemAIModels` capabilites.
4. Call `AppNotificationManager.Register` (In `OnLaunched` before window activation) and/or `AppNotificationManager.Show`.
5. Observe the imminent existence of an exception.

### Expected behavior

A regular Windows notification showing up.

### Screenshots

_No response_

### NuGet package version

2.1.3

### Packaging type

Packaged (MSIX)

### Windows version

Windows 11 version 23H2 (22631, June 2025 Update)

### IDE

Visual Studio 2022

### Additional context

_No response_

Start by reproducing the failure in a packaged WinUI 3 project whose EntryPoint is windows.partialTrustApplication and whose runFullTrust and systemAIModels capabilities are disabled. Trace AppNotificationManager.Register and Show with AppNotificationManager.IsSupported; done means a regular Windows notification appears without either COMException.

Written by the indexing model from the issue text.