A 52-year-old man from Mumbai presents with a 6-month history of a gradually enlarging pigmented lesion on his left shoulder. On examination, the lesion measures 8 mm in diameter with irregular borders, color variation (brown, black, and red areas), and a slightly raised surface. Dermoscopy shows asymmetric pigmentation with atypical network pattern. A full-thickness excisional biopsy confirms cutaneous melanoma with Breslow thickness of 2.8 mm, 3 mitoses per mm², and no ulceration. Sentinel lymph node biopsy of the left axilla is negative. CT chest and abdomen are unremarkable. According to the AJCC 8th edition staging system, what is the stage of this melanoma?