{
  "whole_frame": "(D,A)\u2192(D+t,A+t) keeps original span and digits fixed; output translates t",
  "fixed_source_anchor": "D fixed, A changes1400; original duration changes and digit branch can change",
  "NT": "6\u219236 hinge and full display move together",
  "carrier": "paired endpoints move together; coefficient sum1",
  "festival": "anchor moves, ordered count prefixes remain fixed"
}