dsh-plugin-mermaid: Render Mermaid charts directly in the DSH chat window

# Introduction When developing agents with DSH (DeepSeek Harness), mermaid code blocks frequently appear in model responses to describe processes, architectures, or state transitions. The DSH web client defaults to treating these as regular code blocks: they feature Shiki syntax highlighting and a Copy button, but the diagram itself is invisible. To verify the accuracy of the diagram, users must copy the source code to an external rendering tool, which disrupts the debugging flow due to constant switching. **dsh-plugin-mermaid** addresses this issue: it renders mermaid code blocks into diagrams within chat messages, while retaining the source code view so it can be switched back to at any time. Below, we introduce its features, principles, installation, and usage. # What is dsh-plugin-mermaid