Codespace: dotnet process not terminating automatically

### Problem
Labs is designed to be run in a GitHub Codespaces. That means when the user is able to select a Lab project from the "Run" dropdown, and upon running, build and view a sample in the browser.

However, there's a bug which prevents this from being done more than once without manually running `killall dotnet` or rebuilding the codespace.

### Repro steps
1. Open Labs in a Codespace
2. Build and run a sample.
3. Either stop the build with the "Stop" button, or refresh the page.
4. Try to build and run again. You'll be met with an error like "address is in use".