dsh-reasoning-slider: Switching reasoning gears within the DSH model selector

`qjcnmd/dsh-reasoning-slider` is an MIT-licensed DSH plugin designed to address the cumbersome process of configuring reasoning levels when frequently switching models in DeepSeek Harness. This plugin embeds the reasoning level slider directly into the model selector overlay, allowing users to intuitively view supported levels upon selecting a model and switch them in real-time by dragging the slider, with changes taking effect upon release. Additionally, the plugin supports keyboard arrow keys and mouse wheel operations, automatically retaining the current level when switching models. If the target model does not support the current level, it automatically reverts to the default level, significantly reducing operational overhead. Before installation, ensure that `pnpm` and `dsh` are available in the environment, then add the plugin via the `dsh plugin` command from npm or GitHub, and restart the `dsh web`