Stack traces in workflow context

Errors throws inside the workflow context show `evalmachine` in the stack trace, which makes it really hard to actually debug the real source. We need to fix sourcemap tracking through the bundler step so that we can show the correct stack traces here:

<img width="1558" height="578" alt="Image" src="https://github.com/user-attachments/assets/cf1a9817-75f6-4a78-9246-20300c398bf7" />