Function rib_from_profile 

pub fn rib_from_profile(
    solid: &BrepSolid,
    profile: &[NurbsCurve],
    thickness: f64,
    extrude_dir: Vec3,
    depth: f64,
    name: Option<&str>,
) -> Result<BrepSolid, String>

Rib / stiffener (§6.6). Auto-THICKENs an OPEN planar polyline profile (miter-offset each side by ±thickness/2 + straight caps across the two open ENDS → a CLOSED thin loop), extrudes that loop by depth along extrude_dir, then UNIONs the thin slab into solid — the union trims the rib against the part walls automatically. extrude_dir is typically −np (down into the part) or as given. V1 SCOPE: POLYLINE profiles only — arcs/curves and fully collinear chains return a clear Err (documented follow-ups). If the rib misses the solid entirely the boolean’s Err is returned.