docs/p7_tmem_column_layout.md: Verified that tcgen05.ld 32x32b.x8 is
the correct instruction for multi-row softmax. Each call reads 8 KV
positions for 32 rows. No instruction change needed from single-row.
test_p7_multi_row_softmax.py: Tests T=1,4,32,64,128 at various HD and N.
Gate: cos >= 0.999996.
