Joy and sorrow of caregiving at the heart of “The Art of Care”

War. Fear. Illness and death. These crises twine through the braided narratives in Mosaic Theater Company’s “The Art of Care.” But the emphasis in this world premiere is less on trauma than on empathetic human responses to it. A passerby’s offer of first aid to an injured stranger. A refugee mother’s tender cradling of her baby during a dangerous ocean escape. A musician playing a hammered dulcimer for hospital patients.