Composes an event stream into one node tree per document: aliases
are substituted by the nodes they reference (sharing structure),
tags of untagged nodes are resolved against the given schema, and
mapping keys are checked for uniqueness. Anchors are scoped to
their document; redefining an anchor shadows the previous node.
Errors carry the source bounds of the events they refer to; pair
them with the (line break normalized) input via `toParseError` for
a rendered excerpt, or use `parseDocsWith`, which does so.
Totality: total
Visibility: export