dsh-cal2j: Calories to Joules Plugin

The DeepSeek Harness (DSH) plugin `dsh-cal2j` is designed for lightweight unit conversion, enabling local conversion between calories and joules. Implemented purely in Node.js without network requests, it supports fast calculations in offline environments. It relies on core libraries such as `@deepseek-ai/cordis`, and once installed, it can meet physical unit conversion needs, making it suitable for toolchains that require high precision.