Continuum-window systematic half-width for baseline X1D detections. Each point summarizes the central 68% interval across the nine window–initial-width combinations, normalized by the median detected flux. The dashed line at 0.20 marks the adopted maximum fractional half-width for an accepted X1D detection. Final acceptance also requires the criteria in Table 4: baseline and final S/N thresholds, successful baseline S/N, centroid, and fitted-width checks for all nine variants, and the separately extracted S3D cross-product screen.