src/vs/workbench/contrib/notebook/browser/viewModel/cellEdit.ts/JoinCellEdit/redo
class JoinCellEdit:	async redo(): Promise<void> {
		if (!this.editingDelegate.deleteCell) {
			throw new Error('Notebook Delete Cell not implemented for Undo/Redo');
		}

		await this.cell.resolveTextModel();
		this.cell.textModel?.applyEdits([
			{ range: this.inverseRange, text: this.insertContent }
		]);

		this.editingDelegate.deleteCell(this.index, { kind: SelectionStateType.Handle, primary: this.cell.handle, selections: [this.cell.handle] });
		this.cell.focusMode = CellFocusMode.Editor;
	}