Add Map, Set, WeakMap, and WeakSet constructors with prototype methods to the JavaScript engine: - Map: constructor (from iterable), set/get/has/delete/clear, size property, forEach, keys/values/entries iterators. SameValueZero key equality, insertion order preserved. - Set: constructor (from iterable), add/has/delete/clear, size property, forEach, keys/values/entries iterators. SameValueZero value equality, insertion order preserved. - WeakMap: constructor, set/get/has/delete. Keys must be objects. - WeakSet: constructor, add/has/delete. Values must be objects. Internal storage uses indexed entry objects on the GC heap with deleted-slot markers for stable insertion-order iteration. 30 new integration tests covering all methods and edge cases (NaN keys, object keys, chaining, uniqueness, constructor from arrays, insertion order preservation). Also removes Map/Set from test262 unsupported features list. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>