Persistent naming: joint origins on faces and circular ends, and face appearances, store the face's name and find it by name first (a joint whose face is gone reports it instead of attaching elsewhere)

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

crates/doc/src/appearance.rs

@@ -42,6 +42,9 @@ pub struct FaceLook {
     pub body: String,
     pub point: Vec3,
     pub look: Look,
+    /// The face's persistent name (found first).
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub name: Option<String>,
 }
 
 /// The design's appearances.
@@ -123,7 +126,21 @@ impl Document {
     /// assignment to the same face wins.
     pub fn face_colors(&self, b: &crate::ModelBody) -> Vec<(usize, Look)> {
         let mut out: Vec<(usize, Look)> = Vec::new();
-        for (p, look) in self.face_looks(&b.name) {
+        let names = crate::naming::face_names(b);
+        for f in self.appearances.faces.iter().filter(|f| f.body == b.name) {
+            let (p, look) = (f.point, f.look.clone());
+            // By name (every piece of a split face), else by the point.
+            if let Some(n) = &f.name {
+                let stem = crate::naming::strip_piece(n);
+                let hits: Vec<usize> = (0..names.len()).filter(|i| names.get(*i).is_some_and(|x| crate::naming::strip_piece(x) == stem)).collect();
+                if !hits.is_empty() {
+                    for i in hits {
+                        out.retain(|(j, _)| *j != i);
+                        out.push((i, look.clone()));
+                    }
+                    continue;
+                }
+            }
             if let Some(i) = face_index_at(b, p) {
                 out.retain(|(j, _)| *j != i);
                 out.push((i, look));