Function detect_vuv 

pub fn detect_vuv(fft_out: &[Complex<f32>], f0_bin: f32) -> VuvDecisions

Stateless one-shot V/UV convenience wrapper.

Builds a fresh VuvState internally and calls detect_vuv_and_sa with a neutral e_p = 0.5. Discards the spectral amplitudes. Exposed for validators and tests that want a simple “classify this spectrum” call; the encoder itself uses detect_vuv_and_sa directly so that hysteresis + th_max carry across frames.