run_kanban_goal_loop judges every worker turn outside any agent turn, so on a
relay target each judge call 400'd MissingSessionID and the loop burned its
turn budget on transport-failed 'continue' verdicts. Bind kanban:<task_id>
around the call (same shape as the two handoff gates and kanban_specify),
keeping an already-bound scope. Adds one invariant test on the loop.