App update to 1.8-preview1 with errors

### Describe the bug

When updating my app to the newest 1.8-preview1 version I am encountering the following errors:
NETSDK1022: Duplicate 'PRIResource' items were included. [...] `// Not that relevant because of easy fix w/ the property`
NETSDK1022: Duplicate 'Page' items were included. [...] `// Not that relevant because of easy fix w/ the property`
WMC1012: A project cannot have more than one ApplicationXaml item

### Steps to reproduce the bug

1. Setting the version of `Microsoft.WindowsAppSDK` package to `1.8.250814004-preview`
2. `dotnet restore`
3. `dotnet build`

### Expected behavior

A clean compile w/o any unrelated/unexpected error or warning regarding the .NET SDK or ApplicationXaml.

### Screenshots

_No response_

### NuGet package version

Windows App SDK 1.8 Preview 1: 1.8.250814004-preview1

### Packaging type

Unpackaged

### Windows version

Windows 11 version 24H2 (26100, June 2025 Update)

### IDE

Visual Studio 2022-preview

### Additional context

.NET SDK: 9.0.304

I also tried compiling with the `EnableDefaultPriItems` and `EnableDefaultPageItems` set to `false` but then it still throws the error regarding the ApplicationXaml.

The issue affects both the meta package and the individual packages.

Reproduce with Microsoft.WindowsAppSDK 1.8.250814004-preview1, .NET SDK 9.0.304, and Windows 11 24H2 by running dotnet restore followed by dotnet build. Check how the package handles default PRI, Page, and ApplicationXaml items; done means an unpackaged app builds cleanly without the reported duplicate-item or ApplicationXaml errors.

Written by the indexing model from the issue text.