fix(engine): Delete Design handles each listed name once

crates/engine/src/cmd/graph/designs.rs

@@ -145,6 +145,8 @@ pub(super) fn design(s: &mut Session, p: &Value) -> Result<Value> {
         return Ok(json!({ "id": id.0 }));
     }
     if let Some(names) = names_param(p, "delete", C)? {
+        // Each name once: a repeated one would regenerate the graphs using it again.
+        let names: std::collections::BTreeSet<String> = names.into_iter().collect();
         if let Some(n) = names.iter().find(|n| !taken(s, n)) {
             return Err(bad(C, format!("no design named `{n}`")));
         }

crates/engine/src/cmd/graph/tests.rs

@@ -1304,6 +1304,10 @@ fn graph_designs_are_saved_pasted_and_deleted() {
     s.execute("edit.undo", &json!({})).unwrap();
     assert!(series_parts(&s, id, 0).iter().skip(1).all(|n| matches!(n.kind, NodeKind::Group { .. })));
     assert!(s.execute("graph.design", &json!({"delete": "Nope"})).is_err());
+    // A name listed many times deletes once (its graphs regenerate once).
+    s.execute("graph.design", &json!({"delete": vec!["Pill"; 1000]})).unwrap();
+    assert!(s.doc().unwrap().doc.graph_designs.is_empty());
+    assert!(series_parts(&s, id, 0).iter().all(|n| matches!(n.kind, NodeKind::Path { .. })));
 }
 
 #[test]