Bindings between boa-cat (JS engine) and the DOM (html-cat tree) plus fetch (net-cat). v0.4.0 installs `document.cookie` as a boa-cat 0.3 accessor pair: the getter reads a host-supplied projection, the setter records each `document.cookie = ...` RHS string (with attributes intact) into a hidden write log AND updates the visible projection so subsequent reads see the just-written cookie. Hosts call `set_document_cookie` to seed the projection pre-eval and `read_cookie_writes(&heap)` to recover each per-write Set-Cookie-style string post-eval -- preserving `Max-Age` / `Path` / `Domain` / `Secure` / `HttpOnly` semantics across multiple writes in one script. No mut, no Rc/Arc, no interior mutability, no panics. Seventh sub-crate of a Servo-replacement webview runtime targeting Tauri.