message: add ETA to accumulation limit in render stats
diff: @@ -2808,6 +2808,10 @@ void MainWindow::buildWindowRenderingStats()
  frame->currentAccum,
  frame->accumLimit);
  ImGui::ProgressBar(progress, ImVec2(0.f, 0.f), message);
  + auto remaining = frame->accumLimit - frame->currentAccum;
  + auto secondsPerFrame = 1.f / (latestFPS + 1e-6);
  + ImGui::SameLine();
  + ImGui::Text("ETA: %d s", int(remaining * secondsPerFrame));
  }
  ImGui::End();
  