dsh-chatgpt-web: Bridging ChatGPT Web to DeepSeek Harness

The `dsh-chatgpt-web` plugin for DeepSeek Harness (DSH) provides DSH with a zero-cost, OpenAI-compatible interface by reusing free ChatGPT web sessions via local Playwright browser automation. It supports streaming, automatic model detection, and lifecycle management, but is limited to single-tab execution, has no concurrency capability, and is constrained by OpenAI free-tier limits, making it suitable only for use cases such as pure chat and code explanation.