dsh-aurora-skin: Three Hand-Tuned Skins for DeepSeek Harness

The `dsh-aurora-skin` plugin provides three purely CSS token–customized skins for DeepSeek Harness (DSH): Aurora and Hologram for Dark mode, and Paper for Light mode. It implements visual customization by overriding CSS variables without modifying core code, making it easy to restore defaults. Users can install it via the official command or locally, switch skins in settings, and benefit from local hot-reload development support.