[CI Failure] GitHub codeload.github.com rate limiting (429) when downloading actions/download-artifact action archive

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/32181141483
Build error leg: Tests / Hosting.Orleans / Hosting.Orleans (windows-latest)
Pull request: #18554

## Error Message

```
##[warning]Failed to download action 'https://codeload.github.com/actions/download-artifact/zip/'. Error: Response status code does not indicate success: 429 (Too Many Requests). ... ##[error]Failed to download archive 'https://codeload.github.com/actions/download-artifact/...' after 3 attempts.
```

## Description

GitHub codeload.github.com rate limiting (429) when downloading actions/download-artifact action archive

**Type**: infra-failure

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-08-18 | [32181141483](https://github.com/microsoft/aspire/actions/runs/32181141483) | Tests / Hosting.Orleans / Hosting.Orleans (windows-latest) | #18554 |

Start with the linked Actions run 32181141483, focusing on the Tests / Hosting.Orleans / Hosting.Orleans (windows-latest) job and its download-artifact failure. Review the workflow context for PR #18554 and the reported codeload.github.com 429 responses. Done means the affected workflow no longer fails because the action archive cannot be downloaded, with the mitigation verified in a subsequent run.

Written by the indexing model from the issue text.