dsh-winter-car: Winter Car Usage Recommendation Calculator Plugin

`dsh-winter-car` is a pure Node.js plugin designed specifically for the DeepSeek Harness (DSH) ecosystem, used to compute precise winter vehicle recommendations locally based on parameters. The plugin requires no internet connection to run and is suitable for offline or network-limited environments. It depends on `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools`, and the installation command is `dsh plugin add github:uckkk/dsh-winter-car`. After installation, users can directly invoke the `winter_car` tool in a session.