Investigate #191 on macOS: the fork's GraalVM and Kotlin/Native desktop paths #242

Investigation for #191, macOS first: what PMP's sample needs to build each of the fork's desktop paths (GraalVM native-image, Kotlin/Native) from its mavenLocal artefacts; whether the upcall table and PYTHONHOME staging carry over; the first milestone (the notebook E2E passing in a macOS GraalVM native image); and the list of what the fork side needs, for the darkpyonix lead to request. Output: docs/investigations/fork-desktop-paths-macos.md. No code.