Function collect_list_shared

crates/ffi/src/lean_env.rs:592–594

Collect list elements as LeanShared handles for cross-thread use. The caller should have already MT-marked the parent list via `LeanShared::new`, so `lean_mark_mt` on each element is a single `lean_is_st` check (fast no-op).

(list: LeanList<LeanBorrowed<'_>>)

/// Global cache for Names, shared across all threads.
#[derive(Default)]
pub struct GlobalCache {
  names: DashMap<*mut lean_ffi::include::lean_object, Name>,
}

impl GlobalCache {