A 42-year-old woman with bipolar disorder type I has been stable on olanzapine 15 mg daily for 3 years. She now presents with a 12 kg weight gain, fasting blood glucose 128 mg/dL, and triglycerides 320 mg/dL. She remains psychologically well. Which antipsychotic would be the most appropriate switch to maintain mood stabilization while minimizing metabolic adverse effects?