Add a focused reading view to DeepSeek Harness web sessions with dsh-focus-chat

### 翻译版本1（正式技术文档译法）： dsh-focus-chat is a DeepSeek Harness Web GUI plugin maintained by dingyi222666. It adds a "Focused Chat" tab to conversations, folds assistant responses into collapsible summary rows, and lets users focus only on final deliverables such as thinking time consumption, commands and file changes. This article covers the table of contents, installation commands verified on GitHub and npm, capability boundaries and precautions. ### 翻译版本2（更贴合开源项目文档风格）： dsh-focus-chat is a DeepSeek Harness Web GUI plugin maintained by dingyi222666. This plugin introduces a "Focused Session" tab to the chat interface, collapses assistant replies into expandable summary lines, and filters out irrelevant content to only highlight final deliverables including thinking duration, executed commands and file modification records. The article covers the table of contents, verified installation commands from GitHub and npm, as well as the plugin's capability boundaries and usage notes.