Gemma 4 12B: gemma4_12b_qat_decode_int4linsym_msdpa_g8 (higher-occupancy decode bundle)

Gemma 4 12B: gemma4_12b_qat_decode_int8lin_msdpa_g8 (higher-occupancy decode bundle)

Gemma 4 12B: gemma4_12b_qat_decode_int8lin_msdpa (metal-sdpa decode bundle)

initial commit