dsh-caffeine: Caffeine Half-Life Calculation Tool

`dsh-caffeine` is a plugin for DeepSeek Harness (DSH) that calculates the caffeine half-life and provides recommendations. It is implemented purely in Node.js and has no network dependencies. To install it, use the `dsh plugin add` command and ensure that the required dependencies are installed in the environment. Before use, please review the source code for security. The recommendations are for informational purposes only, and any medical concerns should be addressed under professional medical guidance.