A 49-year-old woman with a BMI of 32 kg/m² is newly diagnosed with type 2 diabetes mellitus after a fasting plasma glucose of 9.0 mmol/L and HbA1c of 8.2%. Her eGFR is 90 mL/min/1.73 m² and liver tests are normal. After 3 months of intensive lifestyle modification, her HbA1c is 8.0%. According to Diabetes Canada pharmacologic guidance, what is the most appropriate next step?