feat(linux): add graphical platform services

src/AcDream.App/Rendering/FramePacingWaiterFactory.cs

@@ -0,0 +1,38 @@
+using AcDream.App.Platform;
+
+namespace AcDream.App.Rendering;
+
+internal interface IFramePacingWaiterFactory
+{
+    IFramePacingWaiter Create();
+}
+
+/// <summary>
+/// The sole startup-time platform selector for software frame waits.
+/// Frame policy and deadline behavior remain platform-neutral.
+/// </summary>
+internal sealed class PlatformFramePacingWaiterFactory
+    : IFramePacingWaiterFactory
+{
+    private readonly GraphicalHostOperatingSystem _operatingSystem;
+
+    internal PlatformFramePacingWaiterFactory(
+        GraphicalHostOperatingSystem operatingSystem)
+    {
+        _operatingSystem = operatingSystem;
+    }
+
+    internal static PlatformFramePacingWaiterFactory ForCurrentProcess() =>
+        new(GraphicalHostPlatformServices.DetectOperatingSystem());
+
+    public IFramePacingWaiter Create() =>
+        _operatingSystem switch
+        {
+            GraphicalHostOperatingSystem.Windows =>
+                WindowsHighResolutionFramePacingWaiter.Create(),
+            GraphicalHostOperatingSystem.Linux =>
+                LinuxMonotonicFramePacingWaiter.Create(),
+            _ => throw new ArgumentOutOfRangeException(
+                nameof(_operatingSystem)),
+        };
+}