Function observed_reader_step 

pub fn observed_reader_step<const P: usize, const S: usize>(
    i: ReaderIn<S>,
    s: ObservedReaderState<P>,
) -> (ObservedReaderOut<P>, ObservedReaderState<P>)

Detect ties without changing the adopted R-32 selection policy. This is an explicit opt-in API: callers of reader_step still receive only values.