As reports grow that Kim Jong-un’s teenage daughter could soon be formally designated as his successor — extending the family’s rule to a fourth generation — we’re revisiting a story about the outsiders who watch North Korea when almost no one else can. In a country closed to inspectors and journalists, open-source “tech detectives” comb through satellite images, videos, and propaganda for tiny clues, trying to piece together what the regime is actually doing — and what it wants the world to believe — as it prepares for what could be a historic handoff of power.