The verdict
If you ship code, pick GitHub. Even a solo project benefits from a trail of reviewable changes, and agents that write code need a place where every edit is checked before it ships. If several people in an operations, onboarding or compliance team run the same procedures and you need to show the steps were done, pick Process Street. Do not push people procedures into GitHub Issues, which are not built for approvals and audit trails. Do not push code into Process Street either. If you are a solo operator with a few checklists, Process Street may be more tool than you need, and a plain document may do.