After UMMA (QK GEMM), 4 warps reading TMEM with 32x32b.x8 each
see a different 32-row partition (verified on B200):
Warp 0 → rows 0-31, Warp 1 → rows 32-63, etc.
Lane l in warp w reads row w*32 + l.
This eliminates the broken row_page<<16 addressing and allows:
- T<=32: warp 0 only, 32x32b.x8, each lane = one row
- T>32: 4 warps, each reads its natural 32-row partition
- Epilogue: same partitioning for reading O from TMEM
No s_p_vals buffer. P streamed per K-tile through sPk.