Fix guest shutdown when VideoOut window is closed (#184)

Propagate Silk window close to runtime teardown so audio and CPU workers stop instead of continuing after the presentation window is dismissed.

src/SharpEmu.HLE/HostSessionControl.cs

@@ -0,0 +1,31 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.HLE;
+
+/// <summary>
+/// Lets host-facing libraries (VideoOut, AudioOut) request cooperative guest
+/// shutdown without taking a dependency on SharpEmu.Core.
+/// </summary>
+public static class HostSessionControl
+{
+    private static Action<string>? _shutdownHandler;
+
+    public static void SetShutdownHandler(Action<string>? handler)
+    {
+        Volatile.Write(ref _shutdownHandler, handler);
+    }
+
+    public static void RequestShutdown(string reason)
+    {
+        try
+        {
+            Volatile.Read(ref _shutdownHandler)?.Invoke(reason);
+        }
+        catch (Exception exception)
+        {
+            Console.Error.WriteLine(
+                $"[LOADER][WARN] Host shutdown handler failed: {exception.Message}");
+        }
+    }
+}