Function detect_faces_from_frame 

pub fn detect_faces_from_frame(
    frame: &Frame,
    score_threshold: f32,
    min_area: usize,
    iou_threshold: f32,
    max_detections: usize,
) -> Result<Vec<Detection>, DetectError>

Heuristic face detector over RGB frames using a skin-probability heatmap.

This is a classical CV baseline that does not require a trained model and is intended for camera demos where low-latency face regions are needed.