Kernel: pole-free six-patch spheres; vendored truck-shapeops with robust meshing and nearest-parameter loop projection (sphere and box booleans work); least-squares sphere classification

Oracle: 25/29 (14 and 15 now match Fusion).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

vendor/truck-shapeops/src/healing/split_closed_edges.rs

@@ -0,0 +1,68 @@
+use super::*;
+
+/// Cuts the edge at the middle point of the bounded curve `curve`.
+fn cut_edge<P, C>(
+    vertices: &mut Vec<P>,
+    Edge {
+        vertices: (_, v1),
+        curve,
+    }: &mut Edge<C>,
+) -> Edge<C>
+where
+    C: BoundedCurve<Point = P> + Cut,
+{
+    let (t0, t1) = curve.range_tuple();
+    let t = (t0 + t1) / 2.0;
+    vertices.push(curve.subs(t));
+
+    let v2 = *v1;
+    *v1 = vertices.len() - 1;
+    let v1 = *v1;
+    let curve0 = curve.cut(t);
+    Edge {
+        vertices: (v1, v2),
+        curve: curve0,
+    }
+}
+
+/// Adds cut edges to the vector `edges`.
+fn add_edges<P, C>(vertices: &mut Vec<P>, edges: &mut Vec<Edge<C>>) -> HashMap<usize, usize>
+where C: BoundedCurve<Point = P> + Cut {
+    let len = edges.len();
+    let sub_add_edges = move |i: usize| {
+        let (v0, v1) = edges[i].vertices;
+        if v0 == v1 {
+            let new_edge = cut_edge(vertices, &mut edges[i]);
+            edges.push(new_edge);
+            Some((i, edges.len() - 1))
+        } else {
+            None
+        }
+    };
+    (0..len).filter_map(sub_add_edges).collect()
+}
+
+fn replace_edges(wire: &mut Wire, added: &HashMap<usize, usize>) {
+    let insert_one_edge = |edge: EdgeIndex| {
+        let Some(new_edge_index) = added.get(&edge.index) else {
+            return vec![edge];
+        };
+        let new_edge = EdgeIndex {
+            index: *new_edge_index,
+            orientation: edge.orientation,
+        };
+        match edge.orientation {
+            true => vec![edge, new_edge],
+            false => vec![new_edge, edge],
+        }
+    };
+    let new_wire = wire.iter().copied().flat_map(insert_one_edge).collect();
+    *wire = new_wire;
+}
+
+pub(super) fn split_closed_edges<P, C, S>(shell: &mut Shell<P, C, S>)
+where C: BoundedCurve<Point = P> + Cut {
+    let added = add_edges(&mut shell.vertices, &mut shell.edges);
+    let wire_iter = shell.faces.iter_mut().flat_map(|face| &mut face.boundaries);
+    wire_iter.for_each(|wire| replace_edges(wire, &added));
+}