Seven test modules each built a migrated in-memory store by hand: open, migrate, and (in sharing) wrap it in a Db. local::memory_conn() is that, and open_in_memory uses it too. Each module's db() is now one line, and the schema, Connection and Mutex imports it needed are gone. DRY pass #2, batch 2, F9 (#5372). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>