Vouch request: @purp

[purp]

What do you want to work on?

I want to fix a bug I found while working through the dev setup in CONTRIBUTING.md, filed as #2112

I'm developing on a Mac outside of k8s with Docker installed and Podman not installed. When I ran mise run gateway it failed trying to link openshell-sandbox with a ProcessFdQuotaExceeded error. ulimit -n 500 worked around it, and Claude's analysis is that there's ulimit checks in the VM build path but not in either of the Docker or Podman build paths.

Why this change?

It looks like any new Mac developer using Docker or Podman and going through initial setup will hit this problem.

Checklist

• I wrote this request myself (not AI-generated)
• I have read CONTRIBUTING.md