Add OpenGL capture path for the hooked video mirror

The Present hook never fired in Phantom Brave because it's an OpenGL game
(OPENGL32.dll loaded, IDXGISwapChain::Present calls=0), so the hooked video source
showed no image. Add an OpenGL producer under the video subsystem: inline-hook
gdi32!SwapBuffers + opengl32!wglSwapBuffers (with a re-entrancy guard, since
SwapBuffers calls wglSwapBuffers), glReadPixels the backbuffer, flip it, and upload
it into the same shared keyed-mutex texture the host already samples -- so the host
is unchanged. DXGI games still hit the Present hook; both producers are installed
and whichever the game uses fills the texture.

Validated by opengl_hook_test (real GL context, clears to a known color, reads the
exact pixels back through the shared texture) and against Phantom Brave (SwapBuffers
~75/s, present=0, shared texture 1920x1080, generation advancing). Vulkan
(vkQueuePresentKHR) still needs WGC -- documented. All 7 tests pass.

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

tests/CMakeLists.txt

@@ -85,3 +85,25 @@ target_link_libraries(present_hook_test PRIVATE
 	dxgi)
 
 add_test(NAME present_hook_test COMMAND present_hook_test)
+
+# In-process self-test for the OpenGL capture path. Reuses the shipping
+# opengl_hook.cpp and drives a real OpenGL context in the same process, so it
+# exercises the SwapBuffers hook, the glReadPixels readback, and the upload into
+# the shared texture (opened by name + read back). Skips without GL / D3D11.
+add_executable(opengl_hook_test
+	opengl_hook_test.cpp
+	${CMAKE_SOURCE_DIR}/hook/src/opengl_hook.cpp
+	${CMAKE_SOURCE_DIR}/hook/src/debug_log.cpp
+	${CMAKE_SOURCE_DIR}/hook/src/hook_registry.cpp)
+
+target_include_directories(opengl_hook_test PRIVATE ${CMAKE_SOURCE_DIR}/hook/src)
+
+target_link_libraries(opengl_hook_test PRIVATE
+	coop_common
+	safetyhook::safetyhook
+	d3d11
+	dxgi
+	opengl32
+	gdi32)
+
+add_test(NAME opengl_hook_test COMMAND opengl_hook_test)