Add Promise constructor, prototype methods, and static methods to the JavaScript engine, with a microtask queue for asynchronous execution: - Promise constructor (via JS preamble so executor runs as bytecode) - Promise.prototype.then/catch/finally with chaining - Promise.resolve/reject static methods - Promise.all/allSettled/race/any static methods - Microtask queue: thread-local queue drained after each vm.execute() - VM.call_function: invoke GC-managed functions (native or bytecode) from outside the execution loop, used by microtask drain - SameValueZero key equality preserved, insertion order maintained Internal storage uses hidden properties (__promise_state__, __promise_result__, __promise_reactions__) on GC-heap objects. Promise.prototype stored as a GC root on the VM to survive collection. 29 new integration tests covering resolve/reject, constructor, executor synchronous execution, then chaining, catch/finally, error propagation, Promise.all/race/any/allSettled, identity passthrough, and double-resolve prevention. Removes Promise from test262 unsupported features list. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>