GGUF norm matches llama.cpp policy: F32 master stays F32, BF16
variant keeps source BF16, K-quants fall back to F16 when kernel
rows do not align. No conv override in pick_type.
Conv kernels widen to F16 at load through gf_load_conv (12 sites).
qwen_load_ctw_f32 accepts BF16 source.
TODO upstream GGML: ggml_conv_1d and ggml_conv_1d_dw force F16 on
their im2col output, while conv_2d picks the kernel dtype. This
crashes F32 and BF16 kernels on CPU (im2col only handles F16) and
BF16 on Vulkan (mul_mat refuses BF16 on the operand the kernel
ends up on). Aligning conv_1d on conv_2d removes the workaround.
Pascal