Three frames at once still filled an 8 GB card on the #879 project at
1080p (7.9 GB, the same as no cap); one frame peaked at 6.3 GB and two at
7.0 to 7.8 GB. One matches how the export scheduler in #898 renders image
sequences (one GPU worker, synchronous readback). EFFECTCRAFT_GPU_INFLIGHT
still raises it.