IntrusivePtr<T> is three pointers: object, deleter, LibContext. The default
constructors zero them, the copy constructors copy them and take a reference
on the object, operator-> and operator* return the object, and the destructors
drop a reference and hand the object to the deleter when it was the last one.
The last-reference release of a pointer without a deleter needs the object's
destructor and the LibContext memory pool and still throws.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>