JS iterator works bad with picture that use multiple sources

Done, check please.

Simplified Iterator Approach

(function (Drupal) {
  Drupal.behaviors.smartImagingStyles = {
    attach: function (context, settings) {
      // Process all picture elements
      const pictures = once('smart-imaging-styles', 'picture', context);
      
      pictures.forEach(picture => {
        // Process all source elements within each picture
        const sources = picture.querySelectorAll('source');
        
        sources.forEach(source => {
          // Your processing logic for each source
          const srcset = source.getAttribute('srcset');
          if (srcset) {
            // Apply transformations to each srcset
            const transformedSrcset = this.transformSrcset(srcset);
            source.setAttribute('srcset', transformedSrcset);
          }
        });
      });
    },
    
    transformSrcset: function(srcset) {
      // Your srcset transformation logic here
      return srcset; // Return modified srcset
    }
  };
})(Drupal);