dsh-plugin-audiolib: Play AudioLib.ai ambient music based on DeepSeek Harness session state

dsh-plugin-audiolib is a plugin for DeepSeek Harness (DSH) designed to automatically control ambient background sounds based on the agent's session state. Its audio source comes from AudioLib.ai; a core feature is that it does not abruptly switch tracks during state changes, stopping playback only when explicitly calling `music_stop()`. The plugin provides three tools, `music_play`, `music_stop`, and `music_status`, supporting streaming via `mpv` or `ffplay`, with a fallback to macOS' `afplay` (requiring pre-downloaded tracks) if these players are unavailable. API keys are securely stored in the DSH credential store and feature a network failure backoff retry mechanism. Installation requires pnpm.