Function jural_chain_links 

pub fn jural_chain_links(upstream: &NQuin, downstream: &NQuin) -> bool

A multi-party chain link: a second-order control relation upstream (held by A toward B) governs downstream (a relation held by B toward C). Valid iff upstream is a second-order position AND the pivot matches — A’s counterparty (upstream.object) is the holder of the downstream relation (downstream.subject). Models “A has Power over B’s Duty to C”.