Refuse lead tools that would restart an interrupted or errored agent

internal/store/store.go

@@ -1061,6 +1061,24 @@ func (s *Store) TaskHandoffs(ctx context.Context, taskID string) ([]Handoff, err
 	return handoffs, rows.Err()
 }
 
+func (s *Store) SessionStopped(ctx context.Context, taskID, sessionID string) (bool, error) {
+	stopped := false
+	err := s.db.QueryRowContext(ctx, `
+		SELECT coalesce(json_extract(e.payload, '$.stopped'), 0) = 1 AND NOT EXISTS (
+			SELECT 1 FROM events a
+			WHERE a.task_id = e.task_id AND a.agent_session_id = e.agent_session_id AND a.seq > e.seq
+				AND a.kind = 'inbox.updated' AND json_extract(a.payload, '$.state') = 'answered'
+		)
+		FROM events e
+		WHERE e.task_id = ? AND e.agent_session_id = ? AND e.kind = 'session.state'
+		ORDER BY e.seq DESC LIMIT 1
+	`, taskID, sessionID).Scan(&stopped)
+	if errors.Is(err, sql.ErrNoRows) {
+		return false, nil
+	}
+	return stopped, err
+}
+
 func (s *Store) LeadEvents(ctx context.Context, owner string, after int64, limit int) ([]api.Event, error) {
 	rows, err := s.db.QueryContext(ctx, `
 		SELECT `+eventColumns+`