Completes the FFI plan: U9 adds a Python ctypes smoke harness proving the C ABI from a non-Rust host; U10 adds cross-platform parity CI gates for header drift, codegen drift, panic-unwind, and stub-adapter passthrough; U11 generates the command-backed wrappers from build.rs templates with a committed drift-gated output. The C ABI stays byte-identical and the surface is Windows and Linux ready with no new FFI code.
