dsh-plugin-worktree: Managing Git Worktree in DSH Web UI

`dsh-plugin-worktree` is a plugin that provides workspace management capabilities for the DSH Web UI. It enables creating, switching, and deleting Worktrees through the browser interface without leaving the Web UI. Key features include a Worktree chip when creating a new session, sidebar badge indicators, and a safety confirmation dialog when deleting. The plugin requires dsh, git, and a Node.js environment, supports custom root and Worktrees directories, and can effectively improve development efficiency.