Current task status (e.g., 'pending', 'running', 'waiting', 'success', 'error', 'cancelled').
'pending' means the latest run hasn't started yet. After a queued follow-up,
an earlier run may still be working.
Typed as str rather than a Literal because the LangGraph SDK's
Run.status is str — using a Literal here would require cast at every
SDK boundary.
Beta
'waiting' means the subagent paused for its user (an approval or a
question), who answers it on the subagent's own thread. This may change.
