dsh-visualizer-widget: Inline Conversation Flow Visualization Plugin for DeepSeek Harness

`dsh-visualizer-widget` is a secure plugin that directly renders SVG/HTML source code generated by the DeepSeek Harness model into interactive cards within the conversation flow. The plugin enables rendering through the `render_visual` tool and the `/visual` command, uses an iframe sandbox mechanism to ensure secure isolation, and supports features such as preview, download, screenshot, and source-code switching. In addition, it provides the `get_visualizer_spec` specification to ensure visual consistency and supports per-turn priority rendering through prompt injection. Installation requires specific dependency versions, and the installation command is `dsh plugin --profile web add github:lovezi0/dsh-visualiz`.