dsh-attention-notify: Native Browser Notifications for DeepSeek Harness

The `dsh-attention-notify` plugin is designed to address the issue that DeepSeek Harness (DSH) is prone to missing background tasks, approvals, and session status updates when the page is not visible. By using native browser notifications, it monitors task status, workflow nodes, and background jobs to provide lightweight, desktop-level alerts. After installation, it must be enabled in the settings and browser notification permissions must be granted. This tool does not rely on external services, but it requires the page to remain open, making it suitable for continuously tracking Agent progress in multitasking environments.