Preset K, byte-identical to the previous output in all captured buffers
and the harness image, measured on an RX 7700 XT:
- LDS row padding so WMMA operand loads hit distinct banks
- WGP mode for enc1/enc2/dec1/dec2, ds_bpermute half-wave exchange for
enc0/dec0/dec3, more waves per window in enc4/dec4/dec5
- cheaper operand plumbing in common/wmma_layout.h (packed f16
conversions, no dynamic vector indexing), raw buffer weight loads,
accumulator-init vectors prepared once
- enc1 as a single-buffer recompute layer, dec1 Q/K/V chains split
- dec5 as four dependent phase kernels