Grief has always been the engine of the WandaVision trilogy. It built Westview, the sitcom suburb conjured by a woman who couldn’t let go. It gave Vision the line that became the series’ thesis: grief is love persevering. VisionQuest turned that idea inward, following a synthezoid who had to learn, slowly and painfully, how to mourn.In the last 30 seconds of its finale, it reached outward. Robert Downey Jr.’s Doctor Doom lifted the rubble of…