entity.parent_id -> entity matches every type pair in both directions, and the
discovery loop kept forward whenever reverse also matched — so an array
include compiled as `parent.parent_id = child.id` and every nested list read
back empty. Now cardinality decides: an array lists the children (reverse), a
scalar reaches the parent (forward) — a line's UI can include its invoice. A
single child through this edge is declared as a one-element array, never a
scalar. fixtures/composition.json pins both joins; 1288 library tests pass.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AvkGU4kQ4wsqxHFpXtZKZM
