Setting up releases from CI

Summary

End-to-end CI setup: one API key with write:releases and write:testing, kept as a GitHub environment secret limited to main; JSON bodies sent base64-encoded in a payloadBase64 envelope (compact one-line JSON also accepted); job order (report, upload, gate); copy-paste reusable GitHub Actions workflows for the gate and deployment reports; a hold-off-first rollout; the gate response; GitLab, Jenkins, shell and CLI equivalents.