dsh-nd: NDJSON Transformation Plugin

The `dsh-nd` plugin for DeepSeek Harness (DSH) aims to provide flexible NDJSON data transformation capabilities, following the "everything is a plugin" design philosophy. Maintained by uckkk, it is a lightweight tool implemented in pure Node.js, with no network dependencies, making it suitable for offline environments. It can be installed with `dsh plugin add github:uckkk/dsh-nd`, and used by directly invoking the tools it registers. Note that the plugin runs with the permissions of the current DSH process, so it is recommended to review the source code before deployment to ensure security.