BTW Side Question Panel

`dsh-btw` is a DeepSeek Harness Web client plugin designed to address the issue where temporary follow-up questions in a conversation pollute the main session context. It provides an isolated temporary Q&A environment through an independent branch session and a floating sidebar. Users can invoke the panel with a keyboard shortcut, ask questions using completed answers as reference context, and switch models independently without affecting the progress or state of the main conversation. The plugin runs entirely on the client side and requires a service restart to take effect.