dsh-conversation-quote: Conversation Text Quoting Plugin

`dsh-conversation-quote` is a pure UI plugin designed for DeepSeek Harness Web, intended to solve the workflow interruption caused by manual copying and pasting. It allows users to select any text in a conversation, click the generated "Quote" pill, and create a compact quote label above the input field. Users can manage multiple quote labels, which are automatically merged into a code block when sending a prompt. The plugin has no configuration options, determines quote attribution based on DOM node type, runs entirely in the browser, supports mouse operations, and works out of the box.