Pure, DOM-free traversal over the family graph. Given the relationship
edges and a selected root, highlightLineage returns the active id set
(root + full pedigree upward + full descendant tree downward + every
spouse of those blood people, as active leaves) and a connector
predicate active only when both joined people are active.
The walk is guarded by the accumulating visited set, so cyclic PARENT_OF
data terminates (REQ-STAMMBAUM-04 / AC10). SIBLING_OF and social
relation types are ignored, so collaterals never enter the active set.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
