The schema drift guard covers the prefix-less relations too

SchemaIdentifierDriftCheck decides whether a backtick-quoted identifier is the store’s to police by asking whether it starts with an observed family prefix (SchemaIdentifierDriftCheck.java:163). That predicate is exactly right for the twelve families and exactly wrong for the relations the schema deliberately places outside every family: diagnostic is cited five times across four authored architecture pages (fact-model.adoc:19, fact-model.adoc:45, pipeline-overview.adoc:38, pipeline-overview.adoc:64, typed-rejection.adoc:7), and renaming it would leave every one of those citations stale with the guard silent, which is the drift the guard exists to catch. The fix is small and needs no new source of truth: the exemption roster already enumerates precisely this set, StoreCatalog already carries it, and the scope predicate can read the union of the family prefixes and the exemption rows' relation names. Worth checking at the same time whether the guard should scan the wider authored .adoc surface (docs/history/ cites the schema too) or stay scoped to docs/architecture.