The investigation into the horrific runway collision at LaGuardia Airport entered its third day. While the airport has officially resumed most operations, Runway 4—where an Air Canada Express jet struck a Port Authority fire truck Sunday night—remains a closed investigation site as federal teams work to clear debris and reconstruct the final seconds of the disaster. The collision claimed the lives of both pilots on Flight 8646: Captain Antoine Forest and First Officer Mackenzie Gunther. Both were remembered by colleagues as dedicated young aviators at the start of promising careers…