Function joint_liable_members 

pub fn joint_liable_members(
    members: &[u64],
    content: u64,
    facts: &[NQuin],
    out: &mut [u64],
) -> usize

Shared liability: if the joint obligation is NOT discharged, every member shares liability — write them into out and return the count. Returns 0 when discharged (no one is liable). Zero-heap (caller-supplied out).