DeepSeek Harness Plugin: dsh-plugin-preflight Preflight Tool

`dsh-plugin-preflight` is a zero-dependency DeepSeek Harness plugin designed to automate the compliance validation of DSH plugins. It checks the `dsh.bundle` configuration, `cordis.patch.yml` mounting, client exports, Peer Dependencies version compatibility, and manifest integrity, preventing plugins from being rejected due to configuration errors. Users can invoke it via the CLI or DSH tools, supporting local and CI environments. The tool has currently been tested only on Windows, and the npm release has not yet been verified.