Bai-2008/dsh-better-panel

Replaces the model button in the DSH composer with its own two-level panel (provider list, then a searchable model list) built around a continuous draggable reasoning-effort slider: blue-to-violet fill, nebula and star particles on higher levels, and a distinct color per level. Picking a model keeps the panel open and moves the slider to that model's middle level. The implementation started from Microqian2th/dsh-codex-effort-slider 1.0.0 (credited in the README); the panel, the seat takeover, the offline test suite and the docs are new here.