Fast Muon optimizer coming to Blackwell consumer GPUs

Tri Dao says a fast Muon optimizer is coming to consumer cards, since its symmetric matmul kernels work once Blackwell consumer GPU mainloop support is in place. Background from @jcz42 reports Gram Newton-Schulz symmetric kernels now support RTX 5090, with 2x faster Newton-Schulz and 1.7x faster optimizer time on 15 layers of Gemma-4 E2B.