v8: composite 0.5203 | GLEU 0.0000 | BERTScore 0.9349 | 1-WER 0.3191 | HumanScore 0.8272 | AIScore 0.1728 | coedit-large r=16 fixed-loss v8-stable-CE [merged]

Auto-upgrade v3: composite 0.8634 | GLEU 0.7593 | BERTScore 0.9758 | 1-WER 0.8552 | r=16, 256-token ctx, C4-GEC data, faithfulness gate [merged weights → merged/]