dsh-acp-adapter: Using ACP Agent in DeepSeek Harness

The `dsh-acp-adapter` plugin enables DeepSeek Harness (DSH) to use ACP Agents directly in the UI. Users need to install the plugin and log in to the Agent CLI, then connect, verify, and switch to the Agent model in DSH to start a session. The plugin supports native session management, automatic tool approval, approval card display, and diagnostic exports. When using it, manage plugin updates manually and ensure that no sensitive information is leaked.