Illustration of the dataset construction workflow. Left column: raw 304 Å observations from SDO/AIA and STEREO/EUVI-A/B. Middle column: preprocessed images after calibration, disk clipping, intensity rescaling, and normalization. Right column: CEA synchronic maps. The upper map shows the input configuration with the STEREO-B coverage gap masked (used as model input), while the lower map shows the corresponding full three-view mosaic serving as the target ground truth.