Move rolling stock and physics into the domain

VehicleDatabase becomes VehicleCatalog, Physics becomes VehiclePhysics, and the
textures.txt and .fiz parsers move to Infrastructure. GameLibrary replaces the
GameData singleton.

StarterNG.Tests/Fakes/InMemoryFileSystem.cs

@@ -92,6 +92,17 @@ public sealed class InMemoryFileSystem : IFileSystem
             .ToList();
     }
 
+    public IReadOnlyList<string> GetFilesRecursive(string path, string searchPattern)
+    {
+        string prefix = Normalize(path) + "/";
+        var pattern = ToRegex(searchPattern);
+        return _files.Keys
+            .Where(key => key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
+            .Where(key => pattern.IsMatch(key[(key.LastIndexOf('/') + 1)..]))
+            .OrderBy(key => key, StringComparer.OrdinalIgnoreCase)
+            .ToList();
+    }
+
     public IReadOnlyList<string> GetDirectories(string path)
     {
         string prefix = Normalize(path) + "/";

StarterNG.Tests/Fakes/TestInstallation.cs

@@ -0,0 +1,48 @@
+using StarterNG.Application;
+using StarterNG.Infrastructure.Adapters;
+using StarterNG.Infrastructure.Sceneries;
+using StarterNG.Infrastructure.Vehicles;
+
+namespace StarterNG.Tests.Fakes;
+
+/// <summary>
+/// The production object graph wired over an in-memory installation: the same
+/// composition as <c>AppServices</c>, with disk, clock and randomness replaced.
+/// </summary>
+public sealed class TestInstallation
+{
+    public const string Root = "game";
+
+    public TestInstallation(InMemoryFileSystem? files = null, DateTime? now = null)
+    {
+        Files = files ?? new InMemoryFileSystem();
+        Paths = new GamePaths(Root);
+        Clock = new FixedClock(now ?? new DateTime(2026, 1, 1, 12, 0, 0));
+        Random = new StubRandom();
+        Log = new FileDiagnosticsLog(Files, Clock, Paths);
+        Strings = new FakeStrings();
+
+        MiniTextures = new MiniTextureIndex(Files, Paths);
+        Physics = new FizPhysicsRepository(Files, Paths, Log);
+        Vehicles = new TexturesTxtVehicleRepository(Files, Paths, Log, new TexturesTxtParser());
+        Sceneries = new SceneryRepository(Files, Paths, Log, new SceneryParser(Clock, Random));
+        MissingAssets = new MissingAssetScanner(Files, Paths);
+        Library = new GameLibrary(Vehicles, Sceneries, MiniTextures, Physics, Log);
+    }
+
+    public InMemoryFileSystem Files { get; }
+    public GamePaths Paths { get; }
+    public FixedClock Clock { get; }
+    public StubRandom Random { get; }
+    public FileDiagnosticsLog Log { get; }
+    public FakeStrings Strings { get; }
+    public MiniTextureIndex MiniTextures { get; }
+    public FizPhysicsRepository Physics { get; }
+    public TexturesTxtVehicleRepository Vehicles { get; }
+    public SceneryRepository Sceneries { get; }
+    public MissingAssetScanner MissingAssets { get; }
+    public GameLibrary Library { get; }
+
+    /// <summary>Path of a file inside the fake installation.</summary>
+    public static string At(params string[] segments) => Path.Combine(new[] { Root }.Concat(segments).ToArray());
+}