feat: add Popov family tree data starting from 1900

fix invariants

chore: consolidate HDS plans and release v0.2.1

docs(rotation): align specs with safe branch rotation

fix(rotation): stabilize safe branch turning and hub routing

feat(rotation): implement hub-centered connected-component rotation; include ancestors + spouses and their descendants; exclude hub descendants; live-edge routing; add debug logs; update tests and docs

docs: update rotation and label specs