My Magento 2 store is already live on a single Nexcess PaaS environment, but every update still goes through a manual FTP-style process. I’d like to replace that with a clean GitHub Actions pipeline that can build, test, and deploy with zero downtime while giving me an easy path to add automated tests later (none exist yet). Here’s what I need you to craft: • A GitHub Actions workflow that checks out the repo, resolves Composer dependencies, runs Magento setup tasks (setup:upgrade, static-content:deploy, di:compile), manages cache/maintenance mode, and deploys to Nexcess over the recommended method (SSH/SFTP or Nexcess API). • Separate branches or job steps that let me push safely to a staging slot before promoting to production, even though Nexcess currently hosts only one environment. If an extra container or sub-domain is required for staging, outline how to configure it. • Rollback logic so a failed deployment automatically restores the previous release. • Environment variables and secrets handled through GitHub Secrets. • Brief Markdown README explaining how the workflow is structured, how to trigger it, and how to extend it with unit or integration tests later. Acceptance criteria • Running git push to the main branch builds and deploys to production with no more than a few seconds of customer-visible maintenance. • I can trigger a staging build manually or from a pull request. • All deployment steps execute inside the GitHub Actions logs with clear success/failure messages. • README is clear enough for another developer to replicate the setup on a fresh Nexcess account. You should have a track record with Magento 2, Composer, and GitHub Actions, plus first-hand experience deploying on Nexcess or similar PaaS platforms. If you can deliver a repeatable, bullet-proof workflow, let’s get started right away.