Bindings between boa-cat (JS engine) and the DOM (html-cat tree) plus fetch (net-cat). v0.7.4 ships the `EventTarget` mixin: `addEventListener(type, callback)` queues handlers under a lazy `__listeners__` slot; `removeEventListener` drops them by `Value::PartialEq`; `dispatchEvent(event)` walks the bubble chain via the v0.6.8 `__parent__` backref and invokes each handler through boa-cat 0.7.1's now-public `expression::call_function`. Listener throws are swallowed at the dispatch boundary per DOM spec. Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.