[CI Failure] Flaky: TestingBuilderTests.CrashTests fails intermittently with unhandled InvalidOperationException

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/28948977829
Build error leg or test failing: Tests / Run VS Code extension unit tests (Windows) / `Aspire.Hosting.Testing.Tests.TestingBuilderTests.CrashTests(genericEntryPoint: True, crashArg: "after-build")`
Pull request: #18688

## Error Message

```
System.InvalidOperationException : Crashing: after-build.
at Program.$(String[] args) in /_/tests/TestingAppHost1/TestingAppHost1.AppHost/Program.cs:line 56
at Aspire.Hosting.Testing.DistributedApplicationFactory.ResolveApplicationAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting.Testing/DistributedApplicationFactory.cs:line 60
at Aspire.Hosting.Testing.DistributedApplicationTestingBuilder.SuspendingDistributedApplicationFactory.BuildAsync(CancellationToken cancellationToken) in /_/src/Aspire.Hosting.Testing/DistributedApplicationTestingBuilder.cs:line 214
```

## Description

Flaky: TestingBuilderTests.CrashTests fails intermittently with unhandled InvalidOperationException

**Type**: flaky-test

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-07-08 | [28948977829](https://github.com/microsoft/aspire/actions/runs/28948977829) | Tests / Run VS Code extension unit tests (Windows) | #18688 |

Start with Aspire.Hosting.Testing.Tests.TestingBuilderTests.CrashTests for the genericEntryPoint: True, crashArg: "after-build" case, then inspect the stack-trace locations in tests/TestingAppHost1/TestingAppHost1.AppHost/Program.cs and src/Aspire.Hosting.Testing/DistributedApplicationFactory.cs. Re-run the Windows VS Code extension unit-test job or the named test to reproduce the intermittent failure. Done means the case no longer fails intermittently and the test still verifies the expected crash behavior.

Written by the indexing model from the issue text.