Garbage Collector Redesign and Integration

Boa is an embeddable JavaScript engine written in Rust. JavaScript is garbage collected by specification, meaning the runtime is responsible for managing memory and reclaiming values once they become unreachable. Boa's current collector (boa_gc) works and is well tested, but it was designed for correctness first, and now carries design debt that holds back performance and maintainability. Experimental redesign work is already underway in the separate Oscars repository. This project focuses on evaluating that work, auditing the current design, improving the GC where needed (tracing strategy, allocation model, rooting) and integrating a production ready collector into Boa's runtime, backed by stress tests, benchmarks and documentation covering the design decisions and tradeoffs. Extensions may include incremental or generational collection, GC aware VM optimizations and heap visualization tooling.