  const editor = editorInstances.get(cellId);
            const code = editor ? editor.getValue() : document.getElementById(`editor-${cellId}`).value;
            
            // Update UI to show running state
            cell.classList.add('cell-running');
            cell.classList.remove('cell-completed', 'cell-queued');
            
            // Update execution count
            const execCount = ++executionCount;
            cell.dataset.executionCount = execCount;
            cell.querySelector('.