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>

common/include/coop/protocol.hpp

@@ -12,7 +12,7 @@ namespace coop
 
 // Bump whenever the layout of SharedBlock or CoopPadState changes. The hook
 // refuses to attach to a host with a mismatched version.
-inline constexpr std::uint32_t kProtocolVersion = 11;
+inline constexpr std::uint32_t kProtocolVersion = 12;
 
 // 'COOP' little-endian, used to sanity-check the mapping before trusting it.
 inline constexpr std::uint32_t kProtocolMagic = 0x504F4F43u;
@@ -167,6 +167,7 @@ struct VideoShare
 	std::uint32_t height;
 	std::uint32_t format;                  // DXGI_FORMAT of the shared texture
 	std::uint64_t present_calls;           // cumulative Present() detours (diagnostic)
+	std::int64_t present_qpc;              // QueryPerformanceCounter at the last publish
 };
 
 // --- Mouse + keyboard forwarding -------------------------------------------