Pre-1.0 with no installed base to migrate: REPO_POLICIES.md forbids
adding numbered migration files beyond 001 before a tagged release.
Fold the variant_content table and source_content.last_accessed_at
column (previously 002_cache_eviction.sql) directly into
001_initial_schema.sql and delete the 002 file. The migration runner
is generic over whatever *.sql files exist in schema/, so no runner
code changes are needed.