Sdl backend (#670)

* [audio] added sdl audio backend and in-tree atrac9 decoder

* [input] replaced per-platform pad readers with sdl gamepad input

* [video] added sdl window and host display plumbing

* [gui] added host display options and per-game render settings

* [bink] synced host movie playback to the guest audio clock

* [cpu] hooked windows write faults into guest image tracking

* [perf] added guest and render profiling, reserved host cpu lanes

* [kernel] fixed stale pthread mutex handle alias

* [host] wired the sdl session, save-data paths and project references

* [audio] hoisted ajm trace stackalloc out of its loop

* [video] Add guest image sync setting

* [build] Strip native symbols

* reuse

src/SharpEmu.HLE/Host/IHostWindowInputSource.cs

@@ -0,0 +1,42 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.HLE.Host;
+
+/// <summary>Input snapshots produced by the active host window.</summary>
+public interface IHostWindowInputSource
+{
+    bool HasKeyboardFocus { get; }
+
+    bool IsKeyDown(int virtualKey);
+
+    int GetGamepadStates(Span<HostGamepadState> destination);
+
+    string? DescribeConnectedGamepad();
+
+    void SetRumble(byte largeMotor, byte smallMotor);
+
+    void SetTriggerRumble(byte? leftTrigger, byte? rightTrigger);
+
+    void SetAdaptiveTriggerEffect(
+        HostAdaptiveTriggerEffect? leftTrigger,
+        HostAdaptiveTriggerEffect? rightTrigger);
+
+    void SetLightbar(byte red, byte green, byte blue);
+
+    void ResetLightbar();
+}
+
+/// <summary>Process-wide bridge between the window layer and host input.</summary>
+public static class HostWindowInputSource
+{
+    private static IHostWindowInputSource? _current;
+
+    public static IHostWindowInputSource? Current => Volatile.Read(ref _current);
+
+    public static void Set(IHostWindowInputSource source) =>
+        Volatile.Write(ref _current, source);
+
+    public static void Clear(IHostWindowInputSource source) =>
+        Interlocked.CompareExchange(ref _current, null, source);
+}