NightShift: Audit Gating for Unattended Execution

`nightshift` is a tool in the DSH ecosystem for safeguarding the long-running contracts of unattended agents. It defines goals and constraints through Manifest signing, performs gating checks before execution, and supports checkpoints and automatic rollback during runtime. The tool does not determine task content; instead, it ensures that acceptance criteria are met and generates detailed audit reports. After installation and enabling, the steps `init`, `preflight`, `step`, `acceptance`, and `brief` must be executed in sequence. This plugin depends on Node.js 20, stores logs in the `rewind` directory, and integrates with external systems through specific exit codes.