Koru Standard Library: the `explain` part of list — joined via `~part explain` in list.kz; members land in koru_list. The consumer's explainer — the enforcement half of the facet story. std/refine reports what was DECLARED on a type; this reports what std/list ENFORCES at its boundary: for every `std/list:new(X)` site, the element's met facet is asked from refine's own fold (`metFields`) — the same producer the transform reads, so the report cannot drift from what push actually guards — plus the branch contract the push signature declares (`| ?ok` / `| ?!violated` / `| ?!oom`). One distinct element type and how many `new` sites construct it.

// @retain: explain_list_event is referenced from generated code
// (koruc's koru_explain_gather invokes every discovered [explainer]).
~[comptime|explainer] pub tor explain-list {
    program: std/compiler:*const Program,
    allocator: std.mem.Allocator
} -> ExplainReport