[CI Failure] NuGet.org serving invalid/corrupt package data (non-object JSON or corrupt nupkg)

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/28898685840
Build error leg: Tests / Polyglot SDK Validation / Java SDK Validation
Pull request: #18656

## Error Message

```
The content at 'https://api.nuget.org/v3-flatcontainer/...' is not a valid JSON object. The JSON document is not an object. / Failed to download package '...' from 'https://api.nuget.org/...'. The nupkg at '...' is not valid. Central Directory corrupt.
```

## Description

NuGet.org serving invalid/corrupt package data (non-object JSON or corrupt nupkg)

**Type**: infra-failure

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-07-07 | [28898685840](https://github.com/microsoft/aspire/actions/runs/28898685840) | Tests / Polyglot SDK Validation / Java SDK Validation | #18656 |

Review build 28898685840 and the NuGet URLs in the reported error first. The issue names no repository files, tests, or entry points; it does not define a project-side change, so completion would require identifying an actionable failure or confirming the external response problem is no longer occurring.

Written by the indexing model from the issue text.