GHSA-HP36-V28F-W3R4 flat-to-nested: Prototype pollution in flat-to-nested convert() via __proto__ parent/id key

Summary convert builds the nested tree by using each flat record's id and parent field values directly as object keys, with no guard against proto / constructor / prototype. A record whose parent is the string "proto" makes tempparent resolve to Object.prototype, and the following initPush...