web-api-cat 0.6.7

Bindings between boa-cat (JS engine) and the DOM (html-cat tree) plus fetch (net-cat). v0.6.7 adds `Element.outerHTML` (getter wraps the existing innerHTML serialiser with the element's own tag; setter no-ops pending parent-backref infrastructure) and `Element.replaceChild(newChild, oldChild)` (in-place children-array swap, returns the old child, preserves length). Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.