## Description Validate Mach-O generation, linking, and runtime execution for composite R2R images, covering object emission, dylib linking/signing, symbol layout, and device/simulator runtime behavior. **Tasks:** - [ ] Unit tests for the Mach-O writer - [ ] Build/link tests to produce a composite R2R dylib from Mach-O objects - [ ] Functional test HelloWorld composite with a single assembly - [ ] Functional test HelloWorld composite with multi-assembly