Bringing autodiff and offload into Rust CI

This project brings autodiff and offload into Rust CI by making them buildable and verifiable in the CI pipeline. Autodiff is currently only partially supported in CI, and offload is not yet enabled there at all. The project will focus on the CI and bootstrap changes needed to validate both areas more consistently before merge, including deeper build-system work such as resolving LLVM linking constraints on macOS where required. Deliverables include CI support for autodiff and offload builds and validation, the required bootstrap integration, and supporting infrastructure improvements to keep the workflow reliable and maintainable over time.