dsh-win-toolkit: Windows Native Capability Plugin

The `dsh-win-toolkit` plugin provided by DeepSeek Harness (DSH) uses secure PowerShell scripts to provide agents with core Windows capabilities, including clipboard read/write, system notifications, hosts file reading, and network diagnostics. The toolkit supports operations such as clipboard writing and notifications (permissions required); the remaining functions are read-only. Inputs are transmitted via Base64 encoding to prevent injection. Installation requires executing a specific command and restarting the service, and requires a Windows 10/11, PowerShell 5.1+, and Node.js 22+ environment.