dsh-vision-check: Vision Diopter Calculation Tool

The DeepSeek Harness (DSH) plugin `dsh-vision-check` aims to address the lack of precision in refractive diopter calculations during agent conversations. It provides parameter-based local computation, outputs results and recommendations, and emphasizes that medical content is for reference only and users should follow professional medical advice. Users can install it via a command to quickly obtain standard calculation results within the conversation flow.