corpus (train split only): 548,202 words, 547,556 distinct 8-grams

arm                     gens  hit-rate  mean-longest   max
------------------------------------------------------------
base                     240      0.00           0.0     8
ckpt225                  240      0.12           1.0    10
ckpt300                  240      0.12           1.0    10
ckpt450                  240      0.12           1.1    11
ckpt900                  240      0.22           1.9    11
------------------------------------------------------------
HELD-OUT (never trained)   364      0.12           1.0    12
  ^ the innocent-sample rate: real author text, same register, 112-word chunks.
    THIS is what a candidate is compared against -- not base-unadapted, whose zero
    partly measures `different register` rather than `did not memorise`.

positive control (corpus slice vs corpus): longest = 160 (must be large, else the detector is blind)