Add a composition-root test that builds the provider with ValidateOnBuild to catch missing registrations (without touching the real hardware monitor), plus per-service registration assertions. Add a MainWindowViewModel test that constructs the view model entirely from faked IHardwareMonitorService/ILogger/IRemoteWebServer, proving the testability win. To make that possible, inject the UI DispatcherQueue (captured on the UI thread by the composition factory) instead of calling the static DispatcherQueue.GetForCurrentThread() in the view-model constructor, which threw in the headless test host; the tree-rebuild marshalling now treats a null dispatcher as direct invocation.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>