add back environments so deployments are tracked

[jeffkala]

Final research shows you can use env in legacy GH plan just don't have some of the settings pages.

• Deployments still work — you can POST deployments with any environment string and see them in the repo's deployment history, since that's core repo API with no plan gate.
• You cannot open the environment settings page, so no environment secrets, no required reviewers, no wait timers, no deployment branch policies. Repo- and org-level secrets are your only option, and they're visible to every workflow.
• environment: pypi in a workflow won't gate anything; it just labels the deployment.