The frontend's node lists become node lists, { pos, end, nodes }, the
shape of tsc-ts's NodeList, so that the frontend can later read tsc-ts's
own nodes. AstNode's list getters return an AstNodeList, ts.NodeArray<T>
is that class, and the frontend reads a list's elements through nodes.
The lists already carried their positions on the wire.
The class is the type, not a structural interface, because native code
represents a class and a record differently.
A decoded file keeps each list's nodes array, as before, and each read
of a list field returns a new AstNodeList over it, so the file holds no
more objects than before. nodes keeps its identity; a list object is not
the same object on each read.
The change is mechanical: a type-aware rewrite of each list field read,
plus hand edits where lists are read through casts, generic accessors
or test mocks. The generated getters and types follow from
generate-ts7-ast-schema.mjs. AstFile and Ts7Session drop their unused
listMetadata hook.