pub fn fp4_quant_e4m3_inplace(x: &mut [f32], block: usize)Expand description
2026-09-25: The shims’ fp4_act_quant with e4m3 scales, in place: amax
floored at 6 * 2^-9, scale = amax / 6 rounded through e4m3, values to
e2m1, dequantised and rounded to bf16.