Function ensure_reads_only_logs 

fn ensure_reads_only_logs(
    catalog: &Catalog,
    dependencies: &BTreeSet<CatalogItemId>,
) -> Result<(), Error>

Enforces the introspection-only contract from CuratedMetricSink::source_sql: every relation the definition reads, walking views transitively, must be a log collection.

Checked here against what the definition reads rather than by import kind after optimization: the import split (storage vs index) depends on which indexes the target cluster happens to have, so it gives the same definition different verdicts on different clusters.