dsh-llm-openai-compatible: Universal Plug

`dsh-llm-openai-compatible` is an open-source plugin for DeepSeek Harness, designed to address the integration of models that are not natively supported. Through the OpenAI-compatible protocol, it enables Harness to connect to any local or remote OpenAI-compatible endpoint—such as vLLM, LM Studio, or OpenRouter—without modifying core code. The plugin provides a web-based configuration interface and supports features such as automatic model discovery, optional API keys, and streaming response reading. Users only need to configure the endpoint address, model catalog, and authentication information in Settings to achieve seamless integration. It also supports custom retry policies and integration with the official DeepSeek API.