Add capture pipeline rate + latency metrics to the Video panel

The FPS readout only measured the host's own render rate, hiding capture stutter.
The Video panel now shows a "Pipeline rates" section:
- Tool render (host FPS / frametime, as before);
- hooked source: Game present (/s, from VideoShare.present_calls deltas), Hook
  publish (/s, generation deltas), and capture->display latency avg/min/max ms;
- WGC source: WGC capture (/s) from a new WindowCapture frame-arrival counter
  (game present + latency are n/a, since WGC frames aren't game-timestamped).

Latency uses a system-wide clock: protocol v11->v12 adds VideoShare.present_qpc,
stamped by the hook at publish (publish_video_frame); the host measures
now_qpc - present_qpc per newly published frame, windowed to min/avg/max each second.

Verified: present_hook_test (x64 + x86) now asserts present_qpc is stamped; full
build x64 + x86 clean; ctest x64 9/9, x86 3/3. The live rate/latency numbers need a
real game mirroring to read meaningfully; wiring validated.

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

tests/present_hook_test.cpp

@@ -146,6 +146,7 @@ int main()
 	check(hook::present_calls() >= 3, "Present detour fired");
 	check(hook::present_frames_shared() > 0, "backbuffer copied into the shared texture");
 	check(block->video.generation.load() > 0, "video generation published to IPC");
+	check(block->video.present_qpc > 0, "present QPC stamped for the latency metric");
 	check(block->video.width == kW && block->video.height == kH, "shared dimensions published");
 	check(block->video.format == DXGI_FORMAT_R8G8B8A8_UNORM, "shared format published");