Function list_into_sexp 

fn list_into_sexp(pairs: Vec<(Option<String>, RValue)>) -> SEXP

Build a VECSXP from list pairs, recursing into each child.

Each child SEXP is protect_raw-rooted before the next child allocates — the same GC discipline as AsNamedList::into_sexp (#1030/#1045), required under gctorture. The scope drops once the list is built.