Add mouse + keyboard forwarding (MKB subsystem, opt-in)

Forward the host window's clicks and keystrokes into the injected game so guests
can drive menus / "Press Start" / text entry that a pad can't.

Protocol (v7->v8): new HookSubsys_Mkb and an SPSC MkbRing of MkbEvents in
SharedBlock (host produces, hook consumes); push/pop helpers.

Hook (hook/src/mkb_hook.cpp, new subsystem): a worker-loop pump drains the ring at
~5 ms and PostMessageW's the matching window messages (WM_KEY*/WM_CHAR, mouse
buttons, WM_MOUSEWHEEL) to the game's main window; it also inline-hooks user32
GetAsyncKeyState / GetKeyboardState / GetCursorPos (stdcall trampolines per the x86
rule) to report a synthesized state so polling games react too. Removing the
subsystem clears all synthesized keys (no stuck input).

Host: the Injection panel gets a "Mouse + keyboard forwarding" subsystem toggle
(opt-in, default off -- the toggle is the hook). host/src/inject/mkb_forward.cpp
reads ImGui IO each frame and forwards only when the host window is focused and
ImGui isn't capturing the event; keyboard always, mouse only while mirroring (clicks
+ wheel, not movement). Mouse coords are mapped through the letterbox to game-client
space (host/src/inject/mkb_map.hpp), accounting for WGC-of-decorated-window vs
hooked/borderless. RawInput/DirectInput games are out of scope for this version.

Verified: new mkb_ring_test + mkb_map_test pass; full build x64 + x86 clean; ctest
x64 9/9 and x86 3/3 green (no regression from the protocol bump). The subsystem is
opt-in, so it can't affect existing behavior unless enabled; the end-to-end
click-into-game path needs live Remote Play + a real game to confirm.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

hook/src/dllmain.cpp

@@ -20,6 +20,7 @@
 #include "focus_spoof.hpp"
 #include "hook_registry.hpp"
 #include "ipc_client.hpp"
+#include "mkb_hook.hpp"
 #include "opengl_hook.hpp"
 #include "present_hook.hpp"
 #include "xinput_hook.hpp"
@@ -71,6 +72,7 @@ DWORD WINAPI worker_thread(LPVOID)
 	bool audio_installed = false;
 	bool audio_ring_open = false;
 	bool video_installed = false;
+	bool mkb_installed = false;
 
 	// Each tick, reconcile each subsystem with the host's requested state: install
 	// what's wanted but missing (modules / the game window may appear lazily) and
@@ -147,6 +149,25 @@ DWORD WINAPI worker_thread(LPVOID)
 			coop::hook::logf("worker_thread: video hooks removed (host request)");
 		}
 
+		// --- Mouse + keyboard forwarding ---
+		// Opt-in. When on, the host streams MKB events into the shared ring; we post
+		// them to the game and synthesize polling state. Drained at high rate below.
+		const bool want_mkb = g_ipc.subsystem_install_requested(coop::HookSubsys_Mkb);
+		if (want_mkb && !mkb_installed)
+		{
+			mkb_installed = coop::hook::install_mkb_hooks(g_ipc);
+			if (mkb_installed)
+			{
+				coop::hook::logf("worker_thread: MKB hooks installed");
+			}
+		}
+		else if (!want_mkb && mkb_installed)
+		{
+			coop::hook::remove_mkb_hooks();
+			mkb_installed = false;
+			coop::hook::logf("worker_thread: MKB hooks removed (host request)");
+		}
+
 		if (audio_installed && !audio_ring_open)
 		{
 			const std::wstring name = coop::audio_ring_name(GetCurrentProcessId());
@@ -179,7 +200,17 @@ DWORD WINAPI worker_thread(LPVOID)
 		coop::hook::update_input_diagnostics(g_ipc); // refreshes each tick; registrations can change
 		coop::hook::hook_publish(g_ipc);             // installed-hooks list + call counts
 		g_ipc.heartbeat();
-		Sleep(250);
+
+		// Reconcile ~4x/s, but drain MKB events far more often (input must be
+		// responsive). 50 slices x 5 ms ~= the old 250 ms reconcile period.
+		for (int slice = 0; slice < 50 && g_running.load(std::memory_order_relaxed); ++slice)
+		{
+			if (mkb_installed)
+			{
+				coop::hook::mkb_pump(g_ipc);
+			}
+			Sleep(5);
+		}
 	}
 
 	if (com_ok)
@@ -214,6 +245,7 @@ BOOL APIENTRY DllMain(HMODULE module, DWORD reason, LPVOID reserved)
 			coop::hook::remove_audio_hooks();
 			coop::hook::remove_present_hooks();
 			coop::hook::remove_opengl_hooks();
+			coop::hook::remove_mkb_hooks();
 			coop::hook::hook_registry_reset();
 		}
 		break;