Function neutral_envelope 

pub fn neutral_envelope(
    target: &SpatialTarget,
    facts: &RduChipFacts,
    body: NeutralBody<'_>,
    certificate: Option<&ChoreographyCertificate>,
) -> String

logos.spatial.neutral v2: the lane, the target block derived from the facts, the empty composed-form sections, the lane’s body (the IR itself, every field declaration-ordered — the certificate travels beside it, never inside — or the grid dump), and the certificate summary when the lane proved one.