configureCommon

Configures a RoomDatabase.Builder with standard settings for this project.

All platforms force setSingleConnectionPool. Without it, Room defaults to a 4-reader pool for named databases, and under coroutine cancellation churn (e.g. DB switches via flatMapLatest) the reader-pool permit semaphore can wedge: all reader connections report Free but permits=0, so every read acquisition times out indefinitely ("Error code: 5, Timed out attempting to acquire a reader connection"). Android hit this first; desktop (Flathub, 2026-07-10) reproduced the identical wedge in field logs, so JVM/iOS were moved off the multi-reader pool too. Single-connection eliminates the separate reader permit pool entirely.

For in-memory databases (tests) this is a no-op for pooling — Room already serves name == null databases from a single connection — it just serializes the query dispatcher.