Error: 'Given groups=1, weight [1,1,4], expected input [1,128,4099] to have 1 channels but got 128'
Root cause: kh_pad is (kd, N+pad) = (128, 4099), but weight was (1, 1, 4) with groups=1.
Conv1d requires in_channels == input_channels/groups, so 1 != 128/1.
Fix: expand weight to (kd, 1, conv_kernel_size) and use groups=kd for depthwise conv.
This matches the pattern in qwen3_5.py:212 (_causal_conv1d_fwd) which uses groups=channels.
This was the cause of 'evaluation failed' — GDN crash on first request killed the engine.
b25fc53e5c