DeepSeek Harness Plugin: ds-notify-plugin (Windows Desktop Notifications)

The DeepSeek Harness plugin `ds-notify-plugin` is designed specifically for Windows users to receive completion status notifications during conversation generation. It relies only on built-in system tools, has no third-party dependencies, and is mounted via the Bundle mechanism, so upgrades do not break existing files. Core features include monitoring only the main conversation, displaying conversation titles, merging notifications with 1.5-second debouncing, and compatibility with PowerShell AUMID display. To install, run `dsh plugin --profile web add ds-notify-plugin` and restart; to uninstall, run the corresponding removal command.