* Add result-or-promise (RP) exec model to interpreter (async-first).
* Add centralized table property access with fast misses.
* Update table string keys to be object map.
* Update error contexts to be more consistent and precise.
* Update evaluator to return either values or _Promises_.
* Update func calls, unary and bin operations, and expression lists.
* Update _stdlib_ to the changes and improve errors.
* Add tests to validate async control flow and error contexts.
* Add dedicated benches that isolate the _runtime_ from parsing.
