dsh-fertilizer-npk: Fertilizer NPK Ratio

DeepSeek Harness (DSH) provides the `dsh-fertilizer-npk` plugin for calculating fertilizer NPK ratios. Maintained by uckkk, it returns clear fertilizer blending recommendations based on crop or soil requirements. It supports parameterized inputs to generate specific recommendations, is implemented in pure Node.js, has no network dependencies, and is suitable for local or offline deployment. Users can install it via a command and invoke it within a session, making it suitable for use cases that require specialized agricultural calculation capabilities.