[CI Failure] Flaky: OrphanDetectionEnvironmentTests.Apply_WithNullStartTime_StampsPidOnly fails with Assert.False on macOS

## Build Information

Build: https://github.com/microsoft/aspire/actions/runs/29456677302
Build error leg or test failing: Tests / RabbitMQ.Client.v6 / RabbitMQ.Client.v6 (windows-latest) / `Aspire.Cli.Tests.Processes.OrphanDetectionEnvironmentTests.Apply_WithNullStartTime_StampsPidOnly`
Pull request: #18799

## Error Message

```
Assert.False() Failure
Expected: False
Actual: True
at Aspire.Cli.Tests.Processes.OrphanDetectionEnvironmentTests.Apply_WithNullStartTime_StampsPidOnly() in /Users/runner/work/aspire/aspire/tests/Aspire.Cli.Tests/Processes/OrphanDetectionEnvironmentTests.cs:line 101
```

## Description

Flaky: OrphanDetectionEnvironmentTests.Apply_WithNullStartTime_StampsPidOnly fails with Assert.False on macOS

**Type**: flaky-test

## Occurrences

| Date | Build | Job | PR |
|------|-------|-----|----|
| 2026-07-15 | [29456677302](https://github.com/microsoft/aspire/actions/runs/29456677302) | Tests / RabbitMQ.Client.v6 / RabbitMQ.Client.v6 (windows-latest) | #18799 |

Start in tests/Aspire.Cli.Tests/Processes/OrphanDetectionEnvironmentTests.cs at line 101 and run Apply_WithNullStartTime_StampsPidOnly. Review build 29456677302, including the macOS description and windows-latest job details, to identify the flaky condition; done means the test passes reliably in CI without the Assert.False failure.

Written by the indexing model from the issue text.