NodeKind's reader buffers the fields that come before `type` as
serde_json::Values. VectorCraft writes `type` first, but a crafted file
can put a long array there: a group whose children held 50M numbers before
its type (a 96 KB gzip) peaked at 1.6 GB, and the cost grows with the
array up to MAX_JSON, before any object in it is counted.
The buffer is read through a counting visitor: each JSON value counts
against MAX_BUFFERED_VALUES (32M, 4M on wasm32) as it is read, and values
replayed from the buffer aren't counted twice. load_file reads within it;
the same file is now refused at a 1.1 GB peak.
Don Omondi