A process answers its seat's verbs through one call: caller-named and
unproven subjects, one queue group per seat, reply {result, error, node}.
The rule that a process answers no call (issue 1171 AC3) is replaced by one
that AnswerSeat is the only way to serve. A compare-and-set write on a
process's own state already exists (State.Create, Update).
Builds: design 47 G A-107 (G-20-lead-answers)
Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h