dsh-plugin-better-sidebar-plugin-audio: Audio Preview Plugin

`dsh-plugin-better-sidebar-plugin-audio` resolves the issue of audio files not being rendered by default in DeepSeek Harness (DSH). The plugin enables streaming playback of large files via HTTP Range and provides sidebar features including waveform rendering, full-track and real-time spectrograms, multi-mode playback controls (including A-B looping), and channel switching. After installation, a restart and hard refresh are required for the changes to take effect. It supports various formats, such as MP3 and WAV, greatly improving the development and debugging experience.