Mock game: drive input/focus/MKB hooks + window title; add DetourGate test

- poll_input() each frame (XInputGetState / GetAsyncKeyState / GetKeyboardState /
  GetForegroundWindow), like a real game, so mock_game_test's hook/unhook storm
  actually exercises removing the input/focus/MKB hooks while their detours are in
  flight -- the coverage gap that let those removal races go untested.
- Window title shows the backend + a once-per-second-smoothed fps.
- A vectored-exception crash logger prints the faulting module+offset (named the
  storm's intermittent crashes during this work; inert otherwise).
- detour_gate_test: fast, deterministic guard for DetourGate -- drain() must block
  while a Guard is in flight and return promptly otherwise, plus a concurrency
  stress that asserts no body runs against freed state. (A synthetic install-race
  unit test was tried but flaked on SafetyHook's own enable/disable atomicity under
  ~30M calls/s, unrelated to our code, so the storm is the install/remove guard.)

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

tests/CMakeLists.txt

@@ -38,6 +38,13 @@ add_executable(audio_ring_test audio_ring_test.cpp)
 target_link_libraries(audio_ring_test PRIVATE coop_common)
 add_test(NAME audio_ring_test COMMAND audio_ring_test)
 
+# Unit test for the DetourGate safe-unhook coordinator (hook/src/hook_guard.hpp): drain() must block
+# while a detour Guard is in flight and return promptly otherwise. Fast/deterministic complement to
+# the mock_game_test hook/unhook storm. Header-only (just needs the hook include dir + threads).
+add_executable(detour_gate_test detour_gate_test.cpp)
+target_include_directories(detour_gate_test PRIVATE ${CMAKE_SOURCE_DIR}/hook/src)
+add_test(NAME detour_gate_test COMMAND detour_gate_test)
+
 # Unit test for the MKB event ring (SPSC push/pop, wrap-around, full/empty).
 add_executable(mkb_ring_test mkb_ring_test.cpp)
 target_link_libraries(mkb_ring_test PRIVATE coop_common)
@@ -276,6 +283,7 @@ coop_output_subdir(tests
 	hook_selftest
 	dinput_hook_test
 	audio_ring_test
+	detour_gate_test
 	mkb_ring_test
 	mkb_map_test
 	audio_mix_test