vec_dot_dt3_q8_1 processes a whole 128-element DT3 block per call
(VDR_DT3_Q8_1_MMVQ = 4, QI_DT3 = 4), i.e. the 4 q8_1 chunks it spans,
with one pair of integer accumulators per chunk:
sum_j d8[j] * (d1*sumi1[j] + d2*sumi2[j])
The trit decode reuses ggml_cuda_dt3_get_trit with fully unrolled loops,
so all indices and pow3 factors fold into constants; no __byte_perm or
other NVIDIA-only intrinsics. Enables MUL_MAT in supports_op: ncols_dst
<= 8 takes MMVQ, larger falls back to dequantization + cuBLAS (no MMQ
tile kernel yet).
Millaguie
bc3e949e71