Fixed-unit Kummer twists in the AR16 D4 search: certified twins and negative controls

| This reproducibility note studies fixed-unit Kummer twists in a finite AR16 pilot. It distinguishes three evidence levels: the published w281 same-group pair; a newly certified but previously unpublished p=41 same-group pair; and raw exploratory p=349 and p=173 controls showing that no general class-number or class-group invariance law follows from the pilot. For p=41, a one-sided octic class-group certificate, fully certified proper D4 subfields, explicit norm-one units, and Arb regulator intervals prove Cl(L10)=Cl(L15)=Z/32Z plus Z/4Z and h=128. The package includes scripts, logs, checksums, and a MacBook cross-machine rerun of the lower-bound portion. No priority claim or general invariance theorem is made.