GAZA CITY An Israeli airstrike that killed at least 17 civilians, including eight children, outside a health clinic in central Gaza has emerged as another harrowing symbol of the territory’s deepening humanitarian disaster. The victims, many of them women and children, gathered at a medical facility run by U.S.-based Project HOPE in Deir el-Balah to receive treatment for malnutrition and illness when the explosion struck. Gaza’s civil defense agency said the children were standing in line for