paste-to-workspace: Save pasted or dragged images and any files as session workspace files.

`paste-to-workspace` is a plugin designed specifically for `dsh web`, aiming to address the fragmented operations when handling screenshots and local files in sessions. The plugin supports pasting images via `Cmd/ctrl+V` or dragging arbitrary files into the chat box, automatically saving them to the session workspace `.dsh-paste/` directory and sending the file path to the model. Core features include: arbitrary file drag-and-drop support, image paste preview, file-type-based icon rendering (image thumbnails, other files display RemixIcon icons), clicking a card to download the original file, text-free file sending, automatic adaptation to light and dark themes, automatic cleanup of expired files after 30 days, and optimization of drag-and-drop hint text. Installation depends on `dsh plugin` and pnpm; you can install it by executing the command via the GitHub source.