dsh-gradient: Gradient Color Tool

The DeepSeek Harness plugin `dsh-gradient` is a "fun dressing" plugin maintained by uckkk, providing local, lightweight gradient color generation. It is implemented purely in Node.js, requires no network requests, and can be invoked in a session after installation to generate gradient colors via its tools. Before using it, ensure `@deepseek-ai/cordis` >= 4.0.1 and `@deepseek-ai/dsh-tools` >= 0.1.0-rc.6. The plugin is released under the MIT License and is suitable for local style processing scenarios.