[CI Failure] VS Code extension VSIX packaging fails on Windows unit test job, cascading to all E2E test artifact downloads

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/33086828076
Build error leg: Tests / Run VS Code extension unit tests (Windows)
Pull request: #19730

## Error Message

```
No files were found with the provided path: extension/out/aspire-extension.vsix. No artifacts will be uploaded. Failed steps: Install dependencies, Package VSIX, Assert E2E VSIX contains bridge, Package production VSIX, Assert production VSIX excludes bridge. Job logs unavailable ('Failed to fetch logs for job'). PR only modifies src/Aspire.Cli/Telemetry/CodingAgentDetector.cs and its test, unrelated to VS Code extension build.
```

## Description

VS Code extension VSIX packaging fails on Windows unit test job, cascading to all E2E test artifact downloads

**Type**: infra-failure

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-08-27 | [33086828076](https://github.com/microsoft/aspire/actions/runs/33086828076) | Tests / Run VS Code extension unit tests (Windows) | #19730 |
| 2026-09-08 | [34259343802](https://github.com/microsoft/aspire/actions/runs/34259343802) | Tests / Run VS Code extension unit tests (Windows) / Run VS Code extension unit tests (Windows) | #17742 |

Start with the Tests / Run VS Code extension unit tests (Windows) job and its Install dependencies, Package VSIX, and assertion steps. Check why extension/out/aspire-extension.vsix is not produced or found; done means both VSIX packaging assertions pass and the E2E VSIX artifacts are uploaded for download.

Written by the indexing model from the issue text.