Find nearest common ancestor node

function findLCA(node1, node2) {
  if (!node1 || !node2) return null;
  
  // Use contains API to check containment chains efficiently
  let curr = node1;
  while (curr) {
    if (curr.contains(node2)) return curr;
    curr = curr.parentNode;
  }
  
  curr = node2;
  while (curr) {
    if (curr.contains(node1)) return curr;
    curr = curr.parentNode;
  }
  
  return null;
}

// Example placeholder (requires DOM environment)
// console.log(findLCA(childNodeA, childNodeB));