dsh-localnotify: DSH Local Notification Bar Plugin

`dsh-localnotify` is a DSH client plugin designed to provide a full-screen notification center in the sidebar. It supports three methods—Agent tools, CLI commands, and file writing—and features multi-level visual severity, search and filtering, detail viewing, and automatic cleanup. Data is stored in a local JSON file and synchronized in real time through a polling mechanism, providing a lightweight instant-feedback solution for background tasks.