Internal raw-definition spec gathered by
PtcRunner.Lisp.Prelude.Compiler during its AST walk, before
host-boundary %PtcRunner.Lisp.Prelude.Export{} records are built and
before the callable private env is captured.
Not part of the public prelude artifact — it carries the raw parser forms
(params_form, body_form) that the compiler needs to both build export
metadata and reconstruct definition forms for env capture (fact #6).
metadata_form is the raw {:map, pairs} parser node captured from a
defn/defn- before normalize_meta/1 flattens it into the (lossy,
order-destroying) metadata map. It exists so source discovery can render
the author's metadata Formatter-faithfully with original key order; metadata
(normalized) still drives everything else. Always nil for constants — (def ...) carries no metadata syntax.