Resolves ContentSourceGraphOverlayConfig across configuration layers
(ContentSourceType.Configuration → ContentSource.Configuration → Run Configuration),
applying defaults tailored to whether the target graph is canonical (IsCanon or TargetGraphType === 'Canon').
Resolves
ContentSourceGraphOverlayConfigacross configuration layers (ContentSourceType.Configuration→ContentSource.Configuration→ RunConfiguration), applying defaults tailored to whether the target graph is canonical (IsCanonorTargetGraphType === 'Canon').