exp015_ch package (content-bearing heredity: 5 brackets, content gauge, 20 genomes) + repro retrofit: every package standalone (own harness copies, portable data roots, real CLIs, repro.py loaders, genome-aware reader) - all README snippets verified by execution

exp012_ar: autoregressive differentiation campaign — article, bed, reader, vitals, 48-run ledger, 17 specimens