dsh-thinking-levels-settings: Configure Model Thinking Levels for DSH Web Custom Providers

`dsh-thinking-levels-settings` is a client plugin for DeepSeek Harness (DSH), designed to address the difficulty of carefully managing custom model reasoning levels in the web interface. By adding a "Settings → Thinking Levels" page, it supports configuring reasoning mode, enabled levels, and input capabilities on a per-model basis. It provides preset protocol mappings, a two-level collapsible interface, real-time preview, search and filtering, as well as import and export for configurations. After installation, users can intuitively configure settings in the GUI and persist them to a local file, reducing the barrier to maintaining YAML.