Refactor derived data management in PLib video library manager. Introduce functionality to clear specific types of derived data, including thumbnails, animated previews, perceptual hashes, and technical metadata. Update ILibraryService and LibraryService to support new data usage reporting and reset operations. Revise SettingsViewModel and UI components to reflect these changes, enhancing user control over data management. Update README.md to document new features and usage instructions.

tests/PLib.Tests/ReactiveUiBootstrap.cs

@@ -0,0 +1,24 @@
+using System.Runtime.CompilerServices;
+using ReactiveUI.Builder;
+
+namespace PLib.Tests;
+
+/// <summary>
+/// Brings ReactiveUI up before any test touches a view model.
+/// </summary>
+/// <remarks>
+/// ReactiveUI 24 refuses to serve <c>WhenAnyValue</c> until it has been initialised, and the
+/// application does that in <c>Program.Main</c> — which a test host never runs. Only the core
+/// services are registered here: platform services are about dispatchers and bindings, and a
+/// view model under test has neither.
+/// </remarks>
+internal static class ReactiveUiBootstrap
+{
+    [ModuleInitializer]
+    internal static void Initialize() =>
+        // BuildApp rather than Build: only the former marks ReactiveUI as initialised, and
+        // that flag is exactly what WhenAnyValue checks.
+        RxAppBuilder.CreateReactiveUIBuilder()
+            .WithCoreServices()
+            .BuildApp();
+}