dsh-sign: Pure Node.js Sign Detection Plugin

dsh-sign is a purely Node.js-based sign determination plugin for DeepSeek Harness (DSH). It requires no network requests and is designed to simplify the complexity of handling sign logic for developers in local environments. The plugin depends on `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools`, and supports installation via commands as well as invocation within sessions. Users should pay attention to environment security and the project license when using it.