Phase 2: Present-hook video path (shared-texture mirror)

Add an injected IDXGISwapChain::Present / Present1 hook as a lower-latency,
border-free alternative to WGC. The hook copies the swapchain backbuffer into a
shared keyed-mutex texture (coop_video_<pid>); the host opens it by name and
samples it. New opt-in HookSubsys_Video (protocol v6 -> v7); the Video mirror
panel gains a WGC vs Hooked source toggle that installs/removes the subsystem.

Verified by present_hook_test (drives a real D3D11 swapchain end-to-end and reads
the rendered pixels back through the shared texture) and against Phantom Brave
(D3D9: hook installs cleanly and stays idle, WGC fallback). All 5 tests pass.

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

hook/CMakeLists.txt

@@ -3,6 +3,7 @@ add_library(coop_hook SHARED
 	src/xinput_hook.cpp
 	src/focus_spoof.cpp
 	src/audio_hook.cpp
+	src/present_hook.cpp
 	src/debug_log.cpp
 	src/hook_registry.cpp)
 
@@ -17,7 +18,9 @@ target_link_libraries(coop_hook PRIVATE
 	safetyhook::safetyhook
 	user32
 	ole32
-	mmdevapi)
+	mmdevapi
+	d3d11
+	dxgi)
 
 set_target_properties(coop_hook PROPERTIES OUTPUT_NAME "coop_hook")