dsh-unit: Unit Conversion Plugin

dsh-unit is a pure Node.js unit conversion plugin for DeepSeek Harness (DSH) agents. After installing it with the `dsh plugin add dsh-unit` command, it automatically handles conversions for various physical quantities and data units, including length, weight, and temperature. Users simply ask in the conversation, and the plugin calls the `convert_unit` tool to perform the calculation. It is suitable for agent development scenarios that frequently require unit conversion, but the source code and license should be reviewed before installation.