Test262 Integration:

• Added Test262 as a submodule and integrated it into the test runner, including a new RunnerWorker.js for isolated test execution, configuration files, curated test prefixes, and a manifest-based approach for test discovery and filtering. This allows running a subset of the official ECMAScript conformance tests in the existing Jasmine/JUnit pipeline. [1] [2] [3] [4] [5] [6] [7]

Depends on #346 since these are being tested with latest Xcode 26.4 locally.