dsh-altitude: Altitude Sickness Calculation Tool

The DeepSeek Harness (DSH) plugin `dsh-altitude` is designed to provide local altitude sickness calculation capabilities for geographic information agents. Implemented in pure Node.js and with no network dependencies, it accepts an altitude parameter and returns calculation results and recommendations. It requires the `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools` dependencies and can be installed via `dsh plugin add`. As third-party code, it is recommended to review the source code and license before enabling it.