A 68-year-old ex-smoker (40 pack-years, quit 5 years ago) has chronic cough and exertional dyspnoea. Spirometry confirms COPD with post-bronchodilator FEV1 65% predicted. He has had one mild exacerbation in the last year. According to the 2023 CTS COPD guideline, what is the preferred initial maintenance pharmacologic therapy?