dsh-mermaid-renderer: Rendering Mermaid Diagrams in DeepSeek Harness

`dsh-mermaid-renderer` is a pure frontend plugin for DeepSeek Harness (DSH) that automatically renders Mermaid diagrams in chats. It supports multiple chart types and provides interactive features such as source code viewing, zooming, and fullscreen mode, while remaining dependency-free and using lazy loading. Installation requires dsh version 0.1.0-rc.8 and can be enabled with a pnpm command. It relies on a network CDN by default, so offline environments need to be handled manually.