graph_mega on Hopper requires EXACT node structure match with working
SHA 11b1a1ca9. Two remaining differences caused the hang:
- c51_grad: 18→19 params (restored unused q_mean_ema_ptr)
- HER relabel: (1,1,1)→(32,1,1) (restored warp-parallel launch)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>