Duplicate: Undo and Redo forget the last Duplicate's move

A shape added after an Undo can get an undone copy's id; duplicating it then
used the move measured from the old original.

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

crates/engine/src/cmd/edit.rs

@@ -51,6 +51,8 @@ fn restore(s: &mut Session, redo: bool) -> Result<Value> {
     st.doc = e.doc;
     st.selection = e.selection;
     st.interaction = None;
+    // A later shape can get an undone copy's id: Duplicate starts over with the usual offset.
+    st.last_duplicate = None;
     st.revision += 1;
     Ok(json!({"label": e.label}))
 }

crates/engine/src/tests.rs

@@ -4098,6 +4098,13 @@ fn duplicating_a_moved_copy_repeats_the_move() {
     s.doc_mut().unwrap().selection.shapes = vec![ShapeId(a as u32)];
     let e = dup(&mut s);
     assert_eq!(boxed(&mut s, e), (100.0 + off, 100.0 + off));
+    // Undone, its id can go to a new shape: duplicating that one uses the usual offset too.
+    s.execute("edit.undo", &json!({})).unwrap();
+    let r = s.execute("shape.insert", &json!({"preset": "ellipse", "rect": [400, 300, 40, 40]})).unwrap();
+    let g = r["id"].as_u64().unwrap();
+    assert_eq!(g, e, "the new shape reuses the undone copy's id");
+    let h = dup(&mut s);
+    assert_eq!(boxed(&mut s, h), (400.0 + off, 300.0 + off));
     // After Undo removed that copy, duplicating the last moved copy gets the usual offset too.
     s.execute("edit.undo", &json!({})).unwrap();
     s.doc_mut().unwrap().selection.shapes = vec![ShapeId(d as u32)];