Create a photorealistic fine art portrait of an adult marathon runner seated after training beside a simple concrete wall. The runner wears an unbranded race singlet, hands relaxed on the knees, with realistic sweat sheen, calm direct gaze, and dignified athletic posture. Use a vertical 3:4 frame, 85mm lens, shallow depth of field, sculptural side lighting from a high window, muted teal and warm sand color palette, detailed skin texture, no text, no brand marks, no watermark.