Prod + Dev (PR) Environments

Hi there,

I would like to understand how to achieve the following workflow.

Production Env: Only Deploys main branch.
Development Env: Only Deploys PR branches.

I can see but those docs are sparse. Help would be much appreciated here.

Project ID: 25c13071-6077-466e-bf9b-2e08a6d0c02f
From the dash, i cant seem to control the where ephemeral PR environments grab their env vars from?