dsh-distance-2d: A Pure Node.js Two-Point Distance Calculation Tool

The `dsh-distance-2d` plugin provided by DeepSeek Harness (DSH) is designed to calculate local distances between two points in a two-dimensional plane. It is implemented in pure Node.js, making it lightweight and free of network dependencies, and is suitable for efficient local execution or use in restricted network environments. Once installed, its registered tool can be invoked directly within a session. Before use, ensure that the dependency requirements for `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools` are met.