all3ncn/dsh-better-sidebar-n23: DSH Full Workbench and Shell Refactoring

`all3ncn/dsh-better-sidebar-n23` is a web plugin for DeepSeek Harness (DSH), designed to address the frequent context switching developers experience between conversational interfaces and code environments by refactoring the Shell interface and providing full workbench capabilities. Forked from `omdsh-dev/DSH-better-sidebar`, the plugin integrates multiple features, including file management, code editing, inline previews, a real terminal, Git operations, and background task management. Its core features include an IDE-style layout (such as a VSCode-style activity bar), dual workspace support, session isolation, and an open service-based API that allows third-party plugins to register sidebar pages. Installation requires Node.js >= 20, and note D