BALTIMORE — As the Dali slid out of its berth at the Port of Baltimore in the early hours of March 26, it wasn’t alone. A pair of 5,000-horsepower tugboats guided the massive container ship into the deep channel in the Patapsco River, pointing it toward the Chesapeake Bay as it began its voyage to Sri Lanka. Then, off they went, according to maritime tracking data. If they’d still been with the…