Reject ambiguous origin and construction plane names (#247)

* Reject ambiguous origin and construction plane names

* Reserve origin plane names for construction planes; suggest the other alias

A construction plane can no longer be created with or renamed to XY, XZ, YZ, Top, Front or
Right, so a plane argument can't become ambiguous in new designs. For older designs that
already hold such a plane, the ambiguity error now also names the origin plane's other
alias (XY for Top...). The existing tests build those legacy names directly.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: bherbruck <brennen.herbruck@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/section.rs

@@ -25,6 +25,8 @@ fn section(s: &mut Session, p: &Value) -> Result<Value> {
     // A named plane's world axis: which component of a point lies along its normal.
     let (origin, normal, axis) = match p.get("plane") {
         Some(Value::String(n)) if Plane::named(n.trim()).is_some() => {
+            // Apply the same ambiguity check as modelling commands before treating a name as an origin alias.
+            super::features::plane_param(s, p.get("plane"), cmd)?;
             let pl = Plane::named(n.trim()).ok_or_else(|| bad(cmd, format!("unknown plane `{n}`")))?;
             let normal = pl.normal();
             let axis = [normal.x, normal.y, normal.z].iter().position(|c| c.abs() > 0.5);