Copies CultLib PR #9 (head 84f932ec) tests/vectors/stake_golden.csv unmodified and
checks log_weight and split_weight against all 26 rows. 25 match within rounding;
the one sub-unit row differs by design: the arm's cliff at unit is Libby's
min_amount_per_identity = unit, which the vectors do not set.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>