Deduplicate the hook DLL and scrub history from its comments

Consolidate four copies of the keyed-mutex shared-texture setup
(present/opengl/d3d9/vk_capture) into one RAII SharedVideoTexture,
two copies of find_main_window into find_window.hpp, audio_hook's
hand-rolled detour guard into the shared DetourGate, the duplicated
vtable_method into vtable_hook.hpp, and the near-identical
Present/Present1 and SwapBuffers/wglSwapBuffers detour pairs into one
shared body each. The vk_layer and vk_capture_perf_test targets now
compile debug_log.cpp since the shared texture code logs.

Comments no longer narrate the past: drop stress-test/game anecdotes,
"used to"/"the old model" phrasing, plan-step labels, and pointers to
docs that do not exist; fix present_hook.hpp/opengl_hook.hpp claims
that predate the D3D12/D3D9/Vulkan backends. Net -266 lines, no
behavior change (full x64 + x86 suites pass, including the mock-game
hook/unhook storm).

hook/src/find_window.hpp

@@ -0,0 +1,46 @@
+// Locate the game's main window from inside the game process: the largest
+// visible, unowned top-level window the pid owns. Shared by the focus spoof
+// (subclass target) and the MKB forwarder (PostMessage target).
+#pragma once
+
+#include <windows.h>
+
+namespace coop::hook
+{
+
+inline HWND find_main_window(DWORD pid)
+{
+	struct Ctx
+	{
+		DWORD pid;
+		HWND best;
+		long best_area;
+	} ctx{pid, nullptr, 0};
+
+	EnumWindows(
+	    [](HWND hwnd, LPARAM lparam) -> BOOL {
+		    auto* c = reinterpret_cast<Ctx*>(lparam);
+		    DWORD pid = 0;
+		    GetWindowThreadProcessId(hwnd, &pid);
+		    if (pid != c->pid || !IsWindowVisible(hwnd) || GetWindow(hwnd, GW_OWNER) != nullptr)
+		    {
+			    return TRUE; // not ours, hidden, or an owned dialog -- keep looking
+		    }
+		    RECT rect = {};
+		    if (!GetWindowRect(hwnd, &rect))
+		    {
+			    return TRUE;
+		    }
+		    const long area = (rect.right - rect.left) * (rect.bottom - rect.top);
+		    if (area > c->best_area)
+		    {
+			    c->best_area = area;
+			    c->best = hwnd;
+		    }
+		    return TRUE;
+	    },
+	    reinterpret_cast<LPARAM>(&ctx));
+	return ctx.best;
+}
+
+} // namespace coop::hook