zuse: ordered-map minor cleanup
?> ?=(^ a)
=^ res acc (f state.acc n.a)
?~ res
- [del=& ..node]
- [del=| ..node(val.n.a u.res)]
+ [del=& this]
+ [del=| this(val.n.a u.res)]
:: +left: recurse on left subtree, copying mutant back into .l.a
::
++ left
