dsh-code-ide: Mount an Optional Browser IDE Workbench in Harness Sessions

dsh-code-ide is an optional client-side plugin (v0.1.0-alpha.0, MIT) maintained by SakalioLabs for the DeepSeek Harness Web profile. It adds an IDE tab at the top of the session, embedding a resource explorer, CodeMirror 6 editor, workspace search, Markdown/media preview, and an xterm.js terminal via same-origin routing, without replacing the Harness chat and trace interface. It is compatible with Harness 0.1.1-rc.2; the recommended installation command is `dsh plugin --profile web add github:SakalioLabs/dsh-code-ide`. The plugin accesses the local workspace with the same permissions as the dsh process and is intended only for local loopback use. Before installation, users should review the source code and security boundary documentation.