v0.54.0

Changed

• replacement is a probability, 0 to 1, instead of on or off: a transfer arriving where its family already has a copy overwrites one resident copy with that probability and is added beside it otherwise, one draw per transfer (per segment at the ordered resolution). --replacement 0.5 on the command line; --replacement alone still means 1 and no flag 0, and True / False still work, so existing runs are byte-identical. genome_summary.json reports, under transfers, how many transfers found a resident copy, replaced it or were added beside it. The nucleotide resolution stays additive. (#476)