DeepSeek Harness Background Image Plugin

The DSH (DeepSeek Harness) plugin `dsh-plugin-background-image` allows users to customize the interface background, supporting web images, local images, and gradient presets. It provides fine-grained controls, including opacity, frosted glass blur, section transparency, content offset, and saturation adjustment. Local images are loaded via a same-origin HTTP service, and configuration settings are saved automatically. The plugin overrides global background tokens and depends on internal class names. Although feature-rich, note that DSH updates may introduce compatibility issues.