Bindings between boa-cat (JS engine) and the DOM (html-cat tree) plus fetch (net-cat). v0.6.2 rounds out structural DOM mutation: `Element.removeChild(child)` drops `child` from `this.children` and shifts the survivors down; `Element.insertBefore(newNode, referenceNode)` inserts before the reference slot (or appends when `referenceNode` is `null`), shifting subsequent children up. All three mutation methods (`appendChild` from v0.6.1 plus these two) share the new `children_object_of` helper and compose with `extract_document` so the post-mutation tree reaches layout / paint on the next eval pass. Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.