Raise RuntimeError on send/throw of a closed coroutine, track
cr_origin, emit never-awaited warnings through the warnings helper,
and add cr_suspended. Stop treating coroutines as iterable. Warn on
unawaited asyncgen asend/athrow/aclose, match async for TypeError
messages, and attach coroutine method and name getset docs.
Assisted-by: Grok:grok-4.6