Video mirror: frametime + FPS graphs with min/max/avg stats

The mirror renders into the host window, so the host's render frame timing is
the mirror's performance. FrameStats now retains a ~2 s ring of frame-time
samples; the Video mirror panel plots them as a frametime graph (0-33 ms
scale) and an FPS graph (0-144 scale), each with an avg overlay, and prints
avg/min/max for both frametime and FPS underneath.

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

host/src/capture_panel.hpp

@@ -9,6 +9,7 @@
 
 #include "capture/frame_renderer.hpp"
 #include "capture/window_capture.hpp"
+#include "ui/app_chrome.hpp"
 
 namespace coop
 {
@@ -24,12 +25,16 @@ public:
 		target_ = target;
 	}
 
-	void draw_ui();
+	// `stats` are the host's render frame-timing, drawn as the mirror's
+	// frametime / FPS graphs (this window is what the mirror renders into).
+	void draw_ui(const FrameStats& stats);
 
 	// Render thread: draw the mirrored frame as the window background.
 	void render(ID3D11DeviceContext* ctx, std::uint32_t dst_w, std::uint32_t dst_h);
 
 private:
+	void draw_perf_graphs(const FrameStats& stats);
+
 	ID3D11Device* device_ = nullptr;
 	FrameRenderer renderer_;
 	WindowCapture capture_;