[CI Failure] Flaky: AtsJavaCodeGeneratorTests probe times out waiting for transport message on ubuntu-latest

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/34401953654
Build error leg or test failing: Tests / No-package tests (regular, Aspire.Hosting.CodeGeneration.Java.Tests, Hosting.CodeGeneration.Java,... / Hosting.CodeGeneration.Java (ubuntu-latest) / `Aspire.Hosting.CodeGeneration.Java.Tests.AtsJavaCodeGeneratorTests.GeneratedReferenceExpression_CancellationIsRequestScoped`
Pull request: #19994

## Error Message

```
Probe failed with exit code 1.
stderr:
Exception in thread "main" java.lang.IllegalStateException: Timed out waiting for transport message
at aspire.ReferenceExpressionCancellationProbe.requireMessage(ReferenceExpressionCancellationProbe.java:148)
at aspire.ReferenceExpressionCancellationProbe.invokeAndComplete(ReferenceExpressionCancellationProbe.java:44)
at aspire.ReferenceExpressionCancellationProbe.main(ReferenceExpressionCancellationProbe.java:29)
```

## Description

Flaky: AtsJavaCodeGeneratorTests probe times out waiting for transport message on ubuntu-latest

**Type**: flaky-test

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-09-09 | [34401953654](https://github.com/microsoft/aspire/actions/runs/34401953654) | Tests / No-package tests (regular, Aspire.Hosting.CodeGeneration.Java.Tests, Hosting.CodeGeneration.Java,... / Hosting.CodeGeneration.Java (ubuntu-latest) | #19994 |

Start with Aspire.Hosting.CodeGeneration.Java.Tests.AtsJavaCodeGeneratorTests.GeneratedReferenceExpression_CancellationIsRequestScoped and the ReferenceExpressionCancellationProbe entry points named in the stack trace. Run the targeted test on ubuntu-latest and trace the transport-message wait; done means the probe completes reliably without timing out.

Written by the indexing model from the issue text.