Support the extended fork's GraalVM native-image and Kotlin/Native desktop paths as user choices #191

What

Support the two extra runtime paths that compose-multiplatform-extended / compose-multiplatform-core-extended provide, as additional choices for users, next to the upstream JetBrains Compose paths that stay the default:

1. GraalVM native-image desktop app: a single executable with the AWT-free window, input, window chrome and resize finished in the fork.
2. Kotlin/Native desktop app: the fork's K/N UI targets with window, input and accessibility moved into the fork.

python-multiplatform should be able to support both: the upcall path is a build-time table with no runtime reflection (AGENTS.md §12.3, §13), which is exactly what a closed-world native image and Kotlin/Native need. The native-image upcall entry point is already verified (docs/platforms/graal-native-image-verification.md), but no Compose window runs through native-image today, and desktop K/N has no interpreter target yet.

Work (once the fork ships the paths)

• Gradle plugin: let an app choose upstream Compose (default), extended GraalVM, or extended K/N; stage PYTHONHOME and the generated tables for each.
• Binder: walk the fork's artefacts (the binder is pinned to upstream Compose today; the fork keeps the public API, so the walk must produce the same bindings; guard with the stub diff in pythonx-compose Binder: public describe_member(kotlin_type_name, member_name) for resolvers #54).
• Desktop Kotlin/Native target for the interpreter (macOS, Linux, mingwX64) if the K/N path needs it.
• sample/: one build per path; the notebook E2E (python-multiplatform-compose/fixtures/notebook-e2e) runs on each.

Requirements already given to the fork side (darkpyonix leader, 2026-10-04)

The upcall table approach stays; no runtime reflection.

When

After torchnative, in python-multiplatform's turn, and after the fork finishes both paths.

Done when

The same pythonx-compose app runs unchanged on upstream Compose, extended GraalVM and extended K/N desktop builds, each with the notebook E2E passing in CI.