[CI Failure] Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests (windows-latest) fails during 'Install sdk for nuget based testing' step

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/34783506552
Build error leg: Tests / Package tests - Windows (class, Aspire.Templates.Tests, Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests (windows-latest))
Pull request: #20021

## Error Message

```
Job 'Tests / Package tests - Windows (class, Aspire.Templates.Tests, Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests (windows-latest))' fails at the 'Install sdk for nuget based testing' step with 'Process completed with exit code 1.'. Job logs unavailable ('Failed to fetch logs for job'). PR only modifies Aspire.Cli backchannel/RunCommand code, unrelated to the templates SDK install pipeline.
```

## Description

Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests (windows-latest) fails during 'Install sdk for nuget based testing' step

**Type**: infra-failure

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-09-13 | [34783506552](https://github.com/microsoft/aspire/actions/runs/34783506552) | Tests / Package tests - Windows (class, Aspire.Templates.Tests, Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests (windows-latest)) | #20021 |

Start with build 34783506552 and the Tests / Package tests - Windows job, focusing on the “Install sdk for nuget based testing” step. Compare the failure with PR #20021, whose changes are reported as unrelated, and investigate the unavailable job logs or equivalent CI output. Done means the SDK installation completes and Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests passes on windows-latest.

Written by the indexing model from the issue text.