dsh-design: Clickable HTML Prototype in DeepSeek Harness

`dsh-design` is a client plugin for DeepSeek Harness that enables agents to generate interactive prototype previews directly by writing HTML. The plugin supports Web, iOS, and Android platforms, provides tools for creation, editing, previewing, and file management, and supports interactions such as zooming, panning, and click-to-pin. Installing the plugin requires restarting DSH. Files are stored in the project directory, with a maximum size of 512 KiB per file.