DeepSeek Harness Plugin: plugin-effort-slider

The DeepSeek Harness plugin `plugin-effort-slider` introduces a reasoning effort adjustment feature that is not natively integrated, optimizing UI interaction by combining the model selector and slider into one. It uses a pill-shaped container, supports a slot-style slider and keyboard navigation, features a top gradient animation effect, and is fully compatible with the DSH theme. The plugin has no core dependencies, supports only the `web` profile, and automatically hides for models that do not support reasoning levels, ensuring safety and compatibility.