Lowe’s Cos. said Monday that Robert Niblock, a 25-year veteran of the home-improvement retailer, plans to retire as chairman, president and chief executive officer. The announcement comes as activist investor D.E. Shaw & Co. pushes the company to close its performance gap with Home Depot Inc. While sales at Lowe’s have risen, they continue to trail gains at its larger competitor. Niblock has led Lowe’s for the last 13 years and will remain in his current roles until a successor is found.