close() now clears _module (initialized to None) inside the active
context together with the function references; lifecycle test asserts
it is retained on failed activation and cleared after close.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
step() reads _dst/_src before the launch; without them the failed-launch
test raised AttributeError instead of the intended RuntimeError.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>