Root cause of garbage output: the GEMM reads scale_a according to
expert_offsets (e.g. [0, 500, 1024, ...]) but scale_a had data at
fixed e*128 offsets. When expert 0 has 500 tokens, the GEMM reads
scale_a[0:500] but only rows 0-127 had valid data.
Fix: pad slot_hidden to num_experts*128 rows (128 per expert) and
pass padded_expert_offsets=[0, 128, 256, ...] to the GEMM. Scale
assembly's fixed 128-row layout now matches the GEMM's expectations.
Padding tokens' GEMM output is discarded (scatter_add only uses
sorted_token_ids for real tokens).
biondizzle
bde81b95f4