dsh-sounds: Add task status sounds to DeepSeek Harness

dsh-sounds is a lightweight plugin designed specifically for the DeepSeek Harness (DSH) web interface, aiming to alert users to task status changes, such as task completion, failure, awaiting approval, and Agent inquiries, through audio cues. Maintained by DNNCOVO, this plugin operates independently and does not rely on other plugins under the MIT license. Its core advantage lies in the absence of external notification tools or pre-recorded audio files; instead, it utilizes the browser-side Web Audio API and oscillators to synthesize specific frequency sound effects in real-time (e.g., an ascending triplet representing completion and a square wave representing an error), thereby reducing resource dependencies. Technically, the plugin subscribes to DSH official service events on the Host side and pushes them to the browser side via SSE endpoints; after the client subscribes, the sound is played immediately. Due to browser autoplay policies...