[CI Failure] GitHub Actions runner fails to parse actions/checkout's action.yml manifest (corrupted download)

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/33046510101
Build error leg: Tests / Build native CLI archive (macOS x64) / Build CLI (osx-x64)
Pull request: #19709

## Error Message

```
##[error]actions/checkout/de0fac2e4500dabe0009e67214ff5f5447ce83dd/action.yml: (Line: 1, Col: 1, Idx: 0) - (Line: 1, Col: 2, Idx: 1): While scanning for the next token, find character that cannot start any token.
##[error]System.ArgumentException: Unexpected type '' encountered while reading 'action manifest root'. The type 'MappingToken' was expected.
Failed to load actions/checkout/de0fac2e4500dabe0009e67214ff5f5447ce83dd/action.yml
```

## Description

GitHub Actions runner fails to parse actions/checkout's action.yml manifest (corrupted download)

**Type**: infra-failure

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-08-27 | [33046510101](https://github.com/microsoft/aspire/actions/runs/33046510101) | Tests / Build native CLI archive (macOS x64) / Build CLI (osx-x64) | #19709 |
| 2026-08-31 | [33428326086](https://github.com/microsoft/aspire/actions/runs/33428326086) | Tests / Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests / Templates-XUnit_Default_NewUpAndBuildSupportProjectTemplatesTests (macos-latest) | #19719 |

Start with build 33046510101 and the listed macOS workflow jobs, then compare their logs with build 33428326086. Investigate how actions/checkout/de0fac2e4500dabe0009e67214ff5f5447ce83dd/action.yml is downloaded and parsed; done means the affected macOS jobs complete without the corrupted-manifest error.

Written by the indexing model from the issue text.