dsh-deepseek-chat: Add an independent "Ask DeepSeek" chat window to the DeepSeek Harness Web UI

dsh-deepseek-chat is a DSH community plugin maintained by lhenlihai-hub (MIT License, v0.2.2). It adds an independent "Ask DeepSeek" chat window to the DeepSeek Harness Web UI, solving the need to ask DeepSeek separately without polluting the main conversation context. The plugin reuses the configured DeepSeek model in dsh (via `ctx.llm`), eliminating the need to enter an API key separately. Core features include opening an independent chat window by clicking on the page's right side, switching between configured models at the top, directly quoting selected text from the main session for questions, supporting streaming output and the thinking process, stopping generation, creating new conversations, and automatically adapting to Chinese/English interfaces and light/dark themes. The plugin conversation and main...