process peri-event --event response aligns to start_time + response_time instead of cue_onset + response_time #176

perievent.event_times places the lever push at start_time + response_time, but response_time is measured from the cue. On go/no-go sessions (cue 5 s after trial start) every --event response window lands 5 s before the push.

Fix: use cue_onset + response_time.