aaronoho/dsh-plugin-selection-comments: Add text selection comments to model output and independent session windows

dsh-plugin-selection-comments brings the text selection and commenting feature from the ChatGPT desktop client, along with a standalone floating chat window, to the DeepSeek Harness Web GUI. After selecting text from the model's output, users can add comments with annotations, which are sent to the model as blockquotes in the next user message. Users can also open a standalone chat window to fork and follow up based on the latest turn without polluting the main conversation. Annotations are stored in the browser's `localStorage`, persisting across refreshes, and are automatically cleared upon successful sending. This is a standard DSH bundle offering three installation methods: `dsh plugin add`, bundle directory installation, and the Desktop profile script. It supports both light and dark themes and accessibility. A complete verification checklist and known limitations are included.