DeepSeek Harness Plugin: dsh-completion-sound

The `dsh-completion-sound` plugin is designed to provide DeepSeek Harness (DSH) with a more robust task feedback mechanism, addressing “waiting-for-confirmation” and “long-task awareness” issues in agent development. It uses WebAudio to synthesize a dual-tone prompt indicating task completion, supports long-task music (10 minutes by default), and enables desktop notifications. Developers can customize special music using files or directories (with a built-in “Guan Yu Song”) and have access to flexible configuration thresholds and volume controls. The plugin disables DSH’s native sounds via `cordis.patch.yml` to avoid conflicts and supports cross-platform notifications on Linux, macOS, and in browsers. Developers can install it using the `dsh plugin` command and configure it on the settings page.