dsh-agent-router: DeepSeek Harness Multi-Model Routing Plugin

The DeepSeek Harness plugin `dsh-agent-router` aims to address the limitations of the main agent when handling specific tasks such as visual recognition and translation. It allows users to define specialized agents and supports multimodal task routing, including image generation and speech transcription, as well as headless CLI subagents. Features include ChatGPT subscription account sign-in, multi-provider API key configuration, account pool health routing, and real-time usage statistics. Users need to configure and enable it via Settings → Agent Routing under DSH ≥ 0.1.5-rc.2.