List: concat/flatten, init, find/find_opt, partition, mapi/iteri,
assoc/assoc_opt. Option: iter/fold/to_list. Result: get_ok/get_error/
map_error/to_option.
Fixed skip-to-boundary! in parser to track let..in / begin..end /
struct..end / for/while..done nesting via a depth counter — without
this, nested-let inside a top-level decl body trips over the
decl-boundary detector. Stdlib functions like List.init / mapi / iteri
use begin..end to make their nested-let intent explicit.
lib/ocaml/runtime.sx defines the stdlib in OCaml syntax (not SX): every
function exercises the parser, evaluator, match engine, and module
machinery built in earlier phases. Loaded once via ocaml-load-stdlib!,
cached in ocaml-stdlib-env, layered under user code via ocaml-base-env.
List: length, rev, rev_append, map, filter, fold_left/right, append,
iter, mem, for_all, exists, hd, tl, nth.
Option: map, bind, value, get, is_none, is_some.
Result: map, bind, is_ok, is_error.
Substrate validation: this stdlib is a nontrivial OCaml program — its
mere existence proves the substrate works.
