Type Alias RowsIter 

pub type RowsIter<'a> = Box<dyn Iterator<Item = RowValue<'a>> + Send + 'a>;

Boxed-iterator alias used at the recursive boundaries (function execution → vector completion → agent completion). One Box per recursive descent, never per leaf row.

Aliased Type

pub struct RowsIter<'a>(/* private fields */);