img-preview: Inline Local Image Preview in DeepSeek Harness

The DeepSeek Harness plugin `img-preview` is designed to address the cumbersome process of displaying local images during AI agent development. It enables AI to render local images directly within the chat dialog by registering tools and loopback routing. Its core features include detecting ` ```img ` fences for inline rendering, supporting multi-image grids and an independent full-screen viewer, and providing the `img_serve` tool to generate accessible URLs. It supports multiple formats such as PNG, JPG, and SVG, while enforcing security restrictions on file size and path. After installation, simply restart the service to use it, significantly improving the interaction experience after a model generates images.