feat: preserve body history and placed modelling workflows

Record ownership transfers in the timeline so earlier Join/Cut membership,
world placement, machining data and styles survive component moves, edits,
independent copying, undo and reopening. Preserve pending positions in history
snapshots and keep constructor transfers ordered during feature redefinition.

Retain shallow sheet pockets and exact planar intersection islands through
unfold/refold, with depth-aware flat previews and DXF export. Store explicit
3D wire coordinate spaces and migrate known legacy provenance without moving
saved points or analytic fits.

Infer unique eligible cylindrical Emboss targets, align Revolve manipulators
with actual extent geometry, and discard obsolete preview errors after input
correction. Certify constructed and immutable imported face styles using exact
source metadata while preserving legacy face names. Upgrade designs to format10
with bounded validation and geometry-preserving legacy migration.

crates/engine/src/cmd/component.rs

@@ -13,6 +13,8 @@ use crate::{Result, Session};
 
 #[path = "component_properties.rs"]
 mod properties;
+#[path = "component_transfer.rs"]
+mod transfer;
 
 #[cfg(test)]
 #[path = "occurrence_tests.rs"]
@@ -133,25 +135,7 @@ fn new_component(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn from_bodies(s: &mut Session, p: &Value) -> Result<Value> {
-    let cmd = "component.from_bodies";
-    let bodies = string_list(p, "bodies");
-    if bodies.is_empty() || bodies.len() > 1000 {
-        return Err(bad(cmd, "`bodies` must list 1…1000 body names"));
-    }
-    let st = s.model.state();
-    for b in &bodies {
-        if st.body(b).is_none() {
-            return Err(bad(cmd, format!("no body `{b}`")));
-        }
-    }
-    let parent = s.active_component;
-    let mut made = Vec::new();
-    for b in bodies {
-        let id = s.doc_mut().add_component(Some(&b), parent)?;
-        s.doc_mut().body_components.insert(b.clone(), id);
-        made.push(json!({"component": id, "body": b}));
-    }
-    Ok(json!({ "components": made }))
+    transfer::from_bodies(s, p)
 }
 
 fn activate(s: &mut Session, p: &Value) -> Result<Value> {
@@ -176,7 +160,7 @@ fn list(s: &mut Session, _p: &Value) -> Result<Value> {
     let st = s.model.state();
     let doc = &s.doc;
     let node = |id: u64, name: &str, parent: Option<u64>| {
-        let bodies: Vec<&str> = st.bodies.iter().filter(|b| doc.body_component(&b.name, b.feature) == id).map(|b| b.name.as_str()).collect();
+        let bodies: Vec<&str> = st.bodies.iter().filter(|b| doc.model_body_component(b) == id).map(|b| b.name.as_str()).collect();
         let features: Vec<&str> = doc
             .features
             .iter()
@@ -223,6 +207,15 @@ fn delete(s: &mut Session, p: &Value) -> Result<Value> {
         return Err(bad(cmd, "the design itself can't be deleted"));
     }
     let gone: Vec<u64> = s.doc.components.iter().filter(|c| s.doc.component_within(c.id, id)).map(|c| c.id).collect();
+    if s.doc.features.iter().any(|feature| {
+        !gone.contains(&feature.component)
+            && matches!(&feature.kind, FeatureKind::BodyTransfer { from, to, .. } if gone.contains(from) || gone.contains(to))
+    }) {
+        return Err(bad(
+            cmd,
+            "component supplies a recorded body transfer outside this subtree; remove that transfer history before deleting its source",
+        ));
+    }
     let feats: Vec<u64> = s.doc.features.iter().filter(|f| gone.contains(&f.component)).map(|f| f.id).collect();
     let d = s.doc_mut();
     for f in &feats {
@@ -241,36 +234,11 @@ fn delete(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn move_bodies(s: &mut Session, p: &Value) -> Result<Value> {
-    let cmd = "component.move_bodies";
-    let to = component(s, p, "component", cmd)?;
-    let bodies = string_list(p, "bodies");
-    let st = s.model.state();
-    if bodies.is_empty() || bodies.iter().any(|b| st.body(b).is_none()) {
-        return Err(bad(cmd, "`bodies` must list existing bodies"));
-    }
-    for b in &bodies {
-        let feature = st.body(b).map(|x| x.feature).unwrap_or(0);
-        let own = s.doc.feature(feature).map(|f| f.component).unwrap_or(0);
-        // The body keeps its place in the world: where it is shown now (its component's frame and
-        // any earlier offset), seen from the new component's frame.
-        let from = s.doc.body_component(b, feature);
-        let now = solvecraft_doc::mat_mul(&s.doc.component_transform(from), s.doc.body_offsets.get(b).unwrap_or(&solvecraft_doc::IDENTITY));
-        let offset = solvecraft_doc::mat_inverse(&s.doc.component_transform(to))
-            .map(|inv| solvecraft_doc::mat_mul(&inv, &now))
-            .unwrap_or(solvecraft_doc::IDENTITY);
-        let doc = s.doc_mut();
-        if own == to {
-            doc.body_components.remove(b);
-        } else {
-            doc.body_components.insert(b.clone(), to);
-        }
-        if solvecraft_doc::is_identity(&offset) {
-            doc.body_offsets.remove(b);
-        } else {
-            doc.body_offsets.insert(b.clone(), offset);
-        }
-    }
-    Ok(json!({"bodies": bodies, "component": to}))
+    transfer::move_bodies(s, p)
+}
+
+pub(crate) fn transfer_constructor_result(s: &mut Session, p: &Value) -> Result<Value> {
+    transfer::move_result(s, p)
 }
 
 fn move_sketches(s: &mut Session, p: &Value) -> Result<Value> {