dsh-reasoning-ruler: Refining a Minimalist Thinking Intensity Selector and Model Selector

`dsh-reasoning-ruler` is a DeepSeek Harness (DSH) web plugin designed to optimize reasoning-intensity control and the model selection experience. Its core feature decouples the reasoning-level selector from the model popover and integrates it into the composer area, displayed as a minimal horizontal line. The plugin supports remembering levels per model, optimistic switching, and automatic rollback. It also improves the model selector's interaction logic, supporting full list expansion, hiding the refresh status, and seat deduplication. After installation, refresh the browser to activate it.