dsh-holdem: Add a 6-player No-Limit Texas Hold'em table in the DeepSeek Harness Web GUI

dsh-holdem is a DSH plugin maintained by BubblePtr (MIT licensed, v0.3.0), designed to provide a six-player No-Limit Texas Hold'em experience where "1 player + 5 LLM agents" interact together for Web GUIs. By adding a "Texas Hold'em" tab to the middle column, the plugin ensures agents only see their own hole cards and that interaction content does not leak reasoning or hand information. Its core features include a poker game engine, the /dsh-holdem/* JSON API, heuristic bot fallback logic when models are unavailable, and browser UI integration based on @deepseek-ai/dsh-client-runtime. Installation is simple, requiring only two commands to add pre-built packages without local compilation. The project's source code structure is clear, including the Node.js engine (src/...)