DeepSeek Harness Plugin: dsh-chatgpt-codex

The `dsh-chatgpt-codex` plugin adds support for ChatGPT and Codex models to DeepSeek Harness (DSH). It utilizes browser callback or device code login, automatically refreshing tokens and managing authentication without relying on `pi-ai`. The plugin is registered as a native `openai-codex` provider, supporting streaming, multi-turn conversations, and multiple models. After installation, it can be run by specifying a profile, and supports checking status, refreshing tokens, and logging out.