[Known Build Error] CppCli tests fail with MSB4278 'Microsoft.Cpp.Default.props'

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1400964
Build error leg or test failing: Microsoft.NET.Build.Tests.dll.4.WorkItemExecution
Pull request: https://github.com/dotnet/sdk/pull/54135

### Known Issue Error Message

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Projects/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": "error MSB4278",
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

## Details

C++/CLI tests like `Microsoft.NET.Build.Tests.GivenThatWeWantToBuildACppCliNonLibraryProject.Given_an_StaticLibrary_project_It_should_fail_with_error_message` fail on `windows.amd64.vs2026.pre.scout.open` Helix queues. The vcxproj fails to import `Microsoft.Cpp.Default.props`:

```
NETCoreCppCliTest.vcxproj(25,3): error MSB4278: The imported file "$(VCTargetsPath)\Microsoft.Cpp.Default.props" does not exist and appears to be part of a Visual Studio component. This file may require MSBuild.exe in order to be imported successfully, and so may fail to build in the dotnet CLI.
```

The test asserts a *specific* failure message (about C++/CLI on the SDK), but the build fails earlier with MSB4278 because the VS 2026 scout image does not provide `$(VCTargetsPath)`/`Microsoft.Cpp.Default.props`. The test sees an unexpected error code and fails, which crashes the helix work item with `BadExit`.

This is the same root-cause family as #53887 (VS 2026 scout images missing C++ tooling) but a different MSBuild error code, so #53887s `Contains` match (`The build tools for Visual Studio 2022 (Platform Toolset = v143) cannot be found`) does not fire here.

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1400964
**Error message validated:** `[error MSB4278`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 4/29/2026 10:09:39 AM UTC

### Report
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|0|0|