Stubs: emit proxy classes with typed members instead of int handles #31

Kotlin-name stubs today annotate every object as int (e.g. def fillMaxWidth(receiver: int, /, fraction: float = ...) -> int), which gives an IDE nothing to complete. pythonx-compose's Pythonic stubs (thisisthepy/pythonx-compose#12) are derived from these, so the type information has to come from the binder, which is where it lives.

Scope (Kotlin names only, as everywhere in the binder):

• one stub class per bound Kotlin type (class Modifier: ...), used in annotations instead of int;
• extension functions also emitted as methods on their receiver's stub class (the runtime already serves them there);
• value classes per the binder's rules; function types as Callable[...];
• overload sets in the binder's _Overloads resolution order.

Completion: for real Compose 1.11.1 jars the stubs type-check a small consumer with mypy (Modifier chain, Checkbox, Text), and a test compares stub signatures to runtime inspect.signature for a sample of declarations.