dsh-luminance: A Relative Luminance Calculation Tool

`dsh-luminance` is a lightweight plugin for DeepSeek Harness (DSH) designed to calculate image relative luminance without network dependencies. Implemented in pure Node, it handles local visual analysis tasks without requiring additional network requests. Developers can install it with the specified command and invoke the relevant tools directly in a session. Because it runs with the current process permissions, reviewing the source code before installation is recommended to ensure compliance and security. It is especially suitable for developers in offline or restricted environments.