Audit found single-column FK woven through ~15-20 sites; earns an
ADR. Decision: reference the parent's full compound PK, matched
positionally to an equal-length child list, per-pair type compat.
DSL `from P.(a,b) to C.(x,y)`; SQL `FOREIGN KEY (x,y) REFERENCES
P(a,b)` with bare-FK auto-expansion. Storage follows the existing
primary_key: [...] list convention (yaml columns: [a,b], uniform
JSON in unchanged metadata TEXT cols); back-compat not required,
so no migration. Also marks T3's verified scope.
claude@clouddev1