Implement a deterministic IntersectionObserver in Happy DOM

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What this task asks for

Implement a real, deterministic IntersectionObserver with async delivery, thresholds, root margins, and target tracking. Implement `observe()`, `unobserve()`, `disconnect()`, and `takeRecords()` with real target tracking. Callback delivery must be asynchronous. Calling `observe()` must not invoke the callback synchronously. Initial observation must queue an entry for each newly observed target. Entries delivered in the same callback cycle must preserve target observation order. `unobserve()` must stop future entries for that target. `disconnect()` must stop future delivery and clear pending records.