Metal FWHT kernels now support block widths up to 8192.

The official source reports this update: b11184: metal: FWHT kernels for block widths above 512. metal: FWHT kernels for block widths above 512 ( #29095 ) metal: FWHT kernels for block widths above 512 The Metal FWHT covers widths 64 to 512, one row per simdgroup with N/32 values per lane. Wider blocks need more registers per lane than that layout allows. kernel_fwht_tg runs one row per threadgroup with 256 threads, so each thread keeps N/256 values. Butterflies below the simdgroup width still shuffle, those up to the threadgroup width go through threadgroup memory, and the rest stay in registers. Same butterfly and sign convention as the simdgroup kernel.