Add VS Code-style three-panel workbench to DeepSeek Harness web interface using dsh-workbench

dsh-workbench is a DeepSeek Harness Web GUI plugin maintained by Dpf555, under the MIT license. It adds a VS Code-style three-panel layout to the web interface: a permanently displayed Explorer on the right, and the Monaco 0.52.2 editor in the middle for file editing and Markdown preview. The installation command for the catalog page is `dsh plugin add github:Dpf555/dsh-workbench`. To get the complete three-panel layout, you also need to download the Monaco resources according to the README and patch the checkout of DSH 0.1.0-rc.6. The plugin runs with the permissions of the current dsh process, so you should check the source code and license before installation.