Gradle plugin: feed PythonStubsTask output to toolchain's typedpythonStubs configuration #27

What

When toolchain's plugin is applied (it creates the typedpythonStubs configuration), python-multiplatform-gradle-plugin adds project.files(<PythonStubsTask output provider>) to it. The task dependency travels with the files, so the type check always sees the current stubs and can never quietly run without them because a path moved.

Why

TypedPython 1b (#20, toolchain issue): the check must see Kotlin-side types through the generated .pyi. The leader required explicit wiring instead of the build/generated/pythonStubs/<sourceSet>/ path convention.

Done when

A plugin test: with the typedpythonStubs configuration present, its files include the stubs task output and resolving them runs the stubs task. With the configuration absent, nothing happens and no error is raised.