Descriptions use change stamps as cache keys

Context

Description resolution combines multiple registries and configuration sources. Stamp changes let a later request use a different cache key.

Decision

Dataset descriptions use local and shared caches keyed by database-maintained change stamps, with cache failures treated as misses rather than requiring explicit invalidation messages.

Alternatives Considered

Broadcast invalidation messages: A lost message could leave a previously cached description in use.

Resolve every description without caching: Repeated queries would reread the same metadata tables.

Consequences

Participating tables need the stamp trigger, including configuration tables owned by other services. The shared stamp writer uses the database definer function. Separate stamp and metadata reads do not establish one consistent database snapshot.