Function argmax_first_wins_f32 

pub fn argmax_first_wins_f32(v: &[f32]) -> u32

2026-09-25: Index of the first maximum of v under strict >.

Two passes: the maximum over 8 lanes plus the remainder, then the first index equal to it. NaN never wins, and empty or all-NaN input returns 0. -0.0 and +0.0 compare equal, so the first of them wins. The server’s verify path calls this (verify_pipeline_helper/argmax.rs), and its tests compare it with a one-loop form.