dsh-window-keeper: Remember the last position and size of DSH desktop windows

The DSH desktop window creation code is hardcoded to 1280x820 and lacks persistence, causing the window to reset to its default size upon every restart. `dsh-window-keeper` is a daemon script that relies solely on Win32 and client-agnostic PowerShell to remember the window's position, size, and maximized state, restoring them on the next launch. The plugin shell is solely responsible for installation, auto-startup, and the settings page toggle. This article covers dual-track installation commands, the `config.json` toggle, the working principle, fallback logic for out-of-bounds or disconnected screen scenarios, known limitations (such as Windows-only support and an approximate 1.2-second jump on startup), and precautions regarding source code verification and the MIT license prior to installation.