A 45-year-old woman with COPD (FEV₁ 45% predicted) has had two moderate exacerbations requiring oral steroids and antibiotics in the past year despite appropriate use of dual long-acting bronchodilators (LAMA/LABA). Her blood eosinophil count is 450 cells/µL. According to Canadian COPD guidelines, which change in inhaler therapy is most appropriate?