dsh-workspace-toolbox: DSH Web Workspace Toolbox

The new `dsh-workspace-toolbox` plugin for DeepSeek Harness (DSH) integrates file browsing, Docker management, Vite project control, and terminal capabilities into the Web UI session view, aiming to reduce context switching during development. It supports workspace file search and preview, Docker image and container management (including SSH connections), automatic Vite project scanning and startup, and multi-terminal support based on xterm.js. Developers need to install pnpm and execute the specified commands to enable the plugin. The changes are client-side and support hot reloading, effectively simplifying DSH-based development and operations workflows.