Function effective_adoption 

pub fn effective_adoption(
    policy: Option<SnapshotAdoption>,
    repo_catalog: Option<&CatalogBounds>,
) -> SnapshotAdoption

The effective adoption policy for a SnapshotPolicy: its own spec.adoption wins; else the target repository’s catalog.adoption; else SnapshotAdoption::Adopt. Neither link is context-free (the repository link resolves per-repo, the policy link per-policy), so neither field carries a schema default — every read goes through this resolver.