WinUI Application Freezes with DirectX Software Rendering

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## Issue Description
When running a WinUI application with DirectX Software Rendering enabled, the application freezes on a blank black screen. This appears to be a regression in Windows App SDK, as the issue occurs after upgrading to 1.6.240829007.

### Environment
- Windows App SDK version: 1.6.240829007
- OS: Windows 11
- Configuration: DirectX Software Rendering mode
- Application type: Standard WinUI 3 application (boilerplate)

### Steps to reproduce the bug

1. Create a basic WinUI 3 application
2. Configure the environment for DirectX Software Rendering
3. Run the application
4. Observe that the application freezes on a blank black screen

### Expected behavior

The application should render correctly in software rendering mode, albeit potentially with lower performance.

### Actual Behavior
The application freezes on a blank black screen with no visible UI elements. No error messages are displayed in the console.

### NuGet package version

Windows App SDK 1.6.0: 1.6.240829007

### Packaging type

Packaged (MSIX)

### Windows version

Windows 11 version 23H2 (22631, November 2023 Update)

### IDE

Visual Studio 2022

### Additional context

- This issue was not present in Windows App SDK 1.4.230822000
- The same application works correctly with hardware rendering
- This appears to be a WinUI-wide issue, as it's reproducible in a minimal boilerplate application without any additional SDKs or dependencies
- When a VSTest is added on top of the application, the error "0x8898008D - No HW rendering device is available for this operation" is observed, further confirming that some component is attempting to use hardware rendering despite software rendering being configured

Start with a minimal packaged WinUI 3 application configured for DirectX Software Rendering and compare behavior between Windows App SDK 1.4.230822000 and 1.6.240829007 on Windows 11 23H2. Confirm the blank-screen freeze and the VSTest error 0x8898008D; done means the minimal application renders its UI correctly in software mode without requiring hardware rendering.

Written by the indexing model from the issue text.