v0.19.4

Fixed

• A value that never reaches the step needing it is caught and re-decided
  (#329). A judge copied the signed-in account id into its output and the
  ticket-creation fan-out read only the items, so every ticket lost its
  assignee while verification passed. Verification now flags a step whose
  code reads a key its bound value cannot hold, and a copied value no later
  step reads. Both, and the agent's own binding proposals, go back to the
  structure pass, which adds the binding when it resolves; the text follows.
  A fan over one field of a result can now read another field of the same
  result as shared (that binding used to be an ambiguity error).