dsh-niao-message: macOS System Notification Plugin for DeepSeek Harness

`dsh-niao-message` is a macOS notification plugin designed for DeepSeek Harness (DSH) to improve awareness of background task status. It maps DSH event streams to the system notification center, triggering banners when tasks encounter exceptions, require action, or complete, and supports clicking notifications to open the app directly. The plugin provides independent configuration for three key scenarios, automatic notification clearing without polling, 3-second throttling and deduplication, and bundled notification binaries. Users can manage settings via a settings panel without manually installing system tools. After installation, notifications are automatically cleared when users return to the DSH page, ensuring lightweight and timely behavior.