agpa-dsh-plugin: Plugin Introduction

agpa-dsh-plugin is a plugin specifically designed for DeepSeek Harness (DSH) to address the challenge of sharing achievement logic across tools. It bridges the AGPA engine, provides a native tool shell, and subscribes to DSH events to automatically track achievement data. Since the AGPA engine and data storage are shared, the plugin can trigger achievements not only in DSH but also in other tools such as Claude Code. It currently supports retrieving statistics and event tagging, and requires Node.js >= 22.