v0.2.4 - drift --anonymize masks array cardinality

Adds an --anonymize flag to bairn drift that replaces "<n=N>"
markers with "<n=*>" in shape signatures, so household-side
cardinality (number of relations, roles) does not leak into
committed baselines. Default stays unchanged; bairn's drift-gate
opts in via .gitlab-ci.yml.

Posture and conditions of use unchanged: NOTICE.md.