Constant MAX_NODES 

pub const MAX_NODES: usize = _; // 1_000_000usize

Default maximum node count for a single Document (matches the reference default in omnist-spec docs/02-document-model.md Sec2.4: a depth limit alone doesn’t bound a shallow-but-enormous document, e.g. a million sibling edges at depth 1). A node is a container (an edge list), as D-9 counts them: keys and scalar values are not nodes. Enforced once, in push, the single arena choke point every construction path (build_node, push_raw) funnels through – see omnist-rs#78. Configurable per read through Limits::max_nodes.