Use new "kira tree" cmd.

data/primbin16.cf

@@ -33,7 +33,8 @@ eval color nclump exact 8
 # draw ring markers for multiple stars,
 # choose marker radius from instantaneous separation * 1.5
 eval kiractl nodes off
-eval kiractl rings on
+eval kiractl rings root
+eval kiractl tree cross 0.5
 eval kiractl ringsize sep
 eval kiractl ringscale 1.5
 ## Could track a particle, with: