fix(database): use a single connection for in-memory test databases

configureCommon() applied setMultipleConnectionPool(maxNumOfReaders = 4)
to every database, including the in-memory ones used by tests. A read on
a pooled reader connection can observe a snapshot older than the latest
write on the writer connection, so a read immediately after a write may
return stale rows.

DeviceLinkRepositoryImplTest.reconcilePrunesShortCodesNoLongerInCatalog
read [a, b] (the pre-prune state) instead of [a] after a deleteNotIn —
passing locally but flaking on CI depending on connection-assignment
timing (failed shard-core on #5738; the identical code passed on #5780).

In-memory builders now pass multiConnection = false so reads serialize
behind writes on one connection. Production/file databases keep the
multi-reader pool.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/database/src/androidMain/kotlin/org/meshtastic/core/database/DatabaseBuilder.kt

@@ -45,7 +45,7 @@ actual fun getDatabaseBuilder(dbName: String): RoomDatabase.Builder<MeshtasticDa
 /** Returns a [RoomDatabase.Builder] configured for an in-memory Android database. */
 actual fun getInMemoryDatabaseBuilder(): RoomDatabase.Builder<MeshtasticDatabase> =
     Room.inMemoryDatabaseBuilder<MeshtasticDatabase>(factory = { MeshtasticDatabaseConstructor.initialize() })
-        .configureCommon()
+        .configureCommon(multiConnection = false)
         .setDriver(BundledSQLiteDriver())
 
 /** Returns the Android directory where database files are stored. */

core/database/src/commonMain/kotlin/org/meshtastic/core/database/MeshtasticDatabase.kt

@@ -139,11 +139,20 @@ abstract class MeshtasticDatabase : RoomDatabase() {
     abstract fun discoveryDao(): DiscoveryDao
 
     companion object {
-        /** Configures a [RoomDatabase.Builder] with standard settings for this project. */
-        fun <T : RoomDatabase> RoomDatabase.Builder<T>.configureCommon(): RoomDatabase.Builder<T> =
-            this.fallbackToDestructiveMigration(dropAllTables = false)
-                .setMultipleConnectionPool(maxNumOfReaders = 4, maxNumOfWriters = 1)
-                .setQueryCoroutineContext(ioDispatcher)
+        /**
+         * Configures a [RoomDatabase.Builder] with standard settings for this project.
+         *
+         * @param multiConnection opens a multi-reader connection pool for concurrent reads. Production/file databases
+         *   want this. In-memory databases (tests) MUST pass `false`: a pooled reader connection can serve a snapshot
+         *   older than the latest write on the writer connection, so a read immediately after a write may observe stale
+         *   rows — making read-after-write assertions non-deterministically flaky (see `DeviceLinkRepositoryImplTest`).
+         *   A single connection serializes reads behind writes.
+         */
+        fun <T : RoomDatabase> RoomDatabase.Builder<T>.configureCommon(
+            multiConnection: Boolean = true,
+        ): RoomDatabase.Builder<T> = this.fallbackToDestructiveMigration(dropAllTables = false)
+            .apply { if (multiConnection) setMultipleConnectionPool(maxNumOfReaders = 4, maxNumOfWriters = 1) }
+            .setQueryCoroutineContext(ioDispatcher)
     }
 }
 

core/database/src/iosMain/kotlin/org/meshtastic/core/database/DatabaseBuilder.kt

@@ -51,7 +51,7 @@ actual fun getDatabaseBuilder(dbName: String): RoomDatabase.Builder<MeshtasticDa
 /** Returns a [RoomDatabase.Builder] configured for an in-memory iOS database. */
 actual fun getInMemoryDatabaseBuilder(): RoomDatabase.Builder<MeshtasticDatabase> =
     Room.inMemoryDatabaseBuilder<MeshtasticDatabase>(factory = { MeshtasticDatabaseConstructor.initialize() })
-        .configureCommon()
+        .configureCommon(multiConnection = false)
         .setDriver(BundledSQLiteDriver())
 
 /** Returns the iOS directory where database files are stored. */

core/database/src/jvmMain/kotlin/org/meshtastic/core/database/DatabaseBuilder.kt

@@ -57,7 +57,7 @@ actual fun getDatabaseBuilder(dbName: String): RoomDatabase.Builder<MeshtasticDa
 /** Returns a [RoomDatabase.Builder] configured for an in-memory JVM database. */
 actual fun getInMemoryDatabaseBuilder(): RoomDatabase.Builder<MeshtasticDatabase> =
     Room.inMemoryDatabaseBuilder<MeshtasticDatabase>(factory = { MeshtasticDatabaseConstructor.initialize() })
-        .configureCommon()
+        .configureCommon(multiConnection = false)
         .setDriver(BundledSQLiteDriver())
 
 /** Returns the JVM/Desktop directory where database files are stored. */