Explicit Resource Management brings scoped cleanup

This is a meaningful quality-of-life upgrade for systems-oriented JavaScript, though it remains opt-in and does not replace careful ownership design.

• –`using` reliably runs cleanup when a block exits, including through exceptions
• –`await using` handles asynchronous teardown without repetitive `try...finally` scaffolding
• –`DisposableStack` and `AsyncDisposableStack` support dynamically assembled resource lifecycles
• –The protocol works across libraries, but APIs must explicitly implement disposal symbols
• –JavaScript aliases and closures can still outlive the binding, so this is not a complete ownership system