Four years ago, Cannes’ Directors’ Fortnight premiered Chilean actor Manuela Martelli ‘s superb directorial debut “Chile ’76,” which tracked with sinister precision the stirring of a complacently bourgeois housewife’s political conscience during the repressive Pinochet regime. Her follow-up, “ The Meltdown ,” now plays in the Un Certain Regard sidebar, but while the filmmaking is just as elegant and the storyline similarly observes sociopolitical upheaval acting on an individual psychology, the result is somewhat less resonant. Perhaps because here, it’s the far more slippery and elusive notion of the nation’s collective silence in the aftermath of its Pinochet trauma that is under the microscope. And perhaps because the subject is a child.  That child is Ines (excellent newcomer Maya O’Rourke), through whose dark, enormous, watchful eyes we observe a drama of disappearance that neatly echoes the stories of forced disappearances under the recently ended dictatorship.…