dsh-ui-task-notify: Web Task Completion Notification Plugin

`dsh-ui-task-notify` is a DeepSeek Harness (DSH) plugin designed to prevent easily missed task-completion and pending-interaction signals when work is running in the background or the page is minimized. It leverages the browser Notification API to trigger system notifications and sounds when an agent finishes work or awaits human intervention (such as approval), without requiring extra UI or RPC. The plugin supports configuration options such as notifying only when the page is hidden and including sub-agent notifications. Developers can install it via npm and must grant notification permissions in their browser.