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/main.cpp

@@ -117,7 +117,7 @@ int run()
 			}
 			if (ui.show_video)
 			{
-				capture.draw_ui();
+				capture.draw_ui(stats);
 			}
 		}
 		else