Pure-virtual declarations (`virtual int read(int key) = 0;`) parse as
field_declaration, not function_definition, so they minted no method node —
calls through an abstract base and cpp-override synthesis had nothing to
attach to. Mirror Java interface methods: mint the node (TS + kernel), mark
isAbstract, and cover with extraction/e2e/parity fixtures.
Co-authored-by: Colby McHenry <colbymchenry@users.noreply.github.com>