Adds optional out_scales[N] (per-output-channel requant scale) to
rkt_npu_matmul; per N-tile it uses the tile's channel scale (exact per-channel
with tile_n=1). This is what gemma4's per-channel weight quantization needs.
Verified on NPU: per-channel test (out_scales[oc]=1/(oc+1)) -> row 144 160 176
192 208 224 240 255 matches CPU exactly. All 5 gemmtest cases pass.
Next U6: ggml glue (Q8_0 weights -> per-oc int8 + per-oc out_scale array;
F32 activations -> int8 + activation scale; call this primitive).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Markus Fritsche
4a0bfcde15