dsh-markstream: A Low-Jitter Streaming Markdown Renderer Built on markstream-react

`dsh-markstream` is a DeepSeek Harness (DSH) web plugin designed to address the jitter issue of the default Markdown renderer. It provides low-jitter incremental streaming rendering through `markstream-react`, supporting code diff comparison, Mermaid diagrams, and KaTeX math formulas. The plugin overrides the system default renderer while preserving specific UI structures such as reasoning blocks and image groups, and can be finely configured via a floating panel in the bottom-right corner. Advanced features require additional dependencies to be installed.