dsh-jimeng: Jimeng Text-to-Image / Image-to-Image Plugin

`dsh-jimeng` is the Jimeng image generation plugin for DeepSeek Harness, supporting text-to-image and image-to-image generation. The plugin provides chat tools and a manual panel, with built-in model detection and configuration. It supports reference images in multiple formats and automatically saves generated images to disk. API keys are stored only on the server side to ensure security. Installation requires Node.js 20 and DSH 0.1.x. Users can obtain API keys from the Volcano Ark console and should note the model differences between Seedream 3.0 and 4.0.