Function label_threshold 

pub fn label_threshold(label: &str) -> f32

Per-label confidence threshold, ported from docling’s LayoutPostprocessor.CONFIDENCE_THRESHOLDS. The raw predictor keeps every detection above the 0.3 base; the postprocessor then drops a cluster whose score is below its label’s threshold. Applying it here (equivalent, since every per-label threshold is ≥ the 0.3 base) keeps low-confidence pictures / tables / list-items out of the assembly, matching docling.