A 58-year-old woman is newly diagnosed with type 2 diabetes mellitus after routine blood tests. HbA1c is 8.2% and fasting plasma glucose is 9.6 mmol/L on two occasions. eGFR is 78 mL/min/1.73 m² and liver enzymes are normal. She has tried diet and exercise for 3 months without improvement. According to Diabetes Canada, which pharmacologic therapy is the most appropriate initial agent?