library: finish the credit query review nits

Put the download-visibility comment on the constant it describes, keep the
no-scan guards beside the seek assertions, and give the identical-sync test a
positive control for both the artist aggregate and the album play recompute.

app/src/main/kotlin/com/subtracks/data/db/LibraryDao.kt

@@ -112,13 +112,13 @@ internal const val CREDITED_ALBUM_ROWS =
         "JOIN albums ON albums.sourceId = songs.sourceId AND albums.id = songs.albumId " +
         "WHERE song_artists.sourceId = :sourceId"
 
-// Download visibility follows the credit path: an album credit includes the album when any song is
-// downloaded, while a track credit includes it only when the credited track is downloaded.
 internal const val ALBUMS_FOR_ARTIST =
     "SELECT albums.* FROM (SELECT DISTINCT albumId FROM ($CREDITED_ALBUM_ROWS) WHERE artistId = :artistId) credits " +
         "JOIN albums ON albums.sourceId = :sourceId AND albums.id = credits.albumId " +
         "ORDER BY year DESC, sortName COLLATE NOCASE, id"
 
+// Download visibility follows the credit path: an album credit includes the album when any song is
+// downloaded, while a track credit includes it only when the credited track is downloaded.
 private const val DOWNLOADED_ARTIST_ALBUMS =
     "SELECT albums.id FROM albums " +
         "WHERE albums.sourceId = :sourceId AND albums.artistId = artists.id " +

app/src/test/kotlin/com/subtracks/data/db/LibraryDaoTest.kt

@@ -871,6 +871,8 @@ class LibraryDaoTest {
                 plan,
                 plan.contains("USING INDEX index_song_artists_sourceId_artistId (sourceId=? AND artistId=?)"),
             )
+            assertFalse(plan, plan.contains("SCAN albums"))
+            assertFalse(plan, plan.contains("SCAN songs"))
         }
 
     private suspend fun plan(sql: String): String =

app/src/test/kotlin/com/subtracks/data/sync/SyncServiceTest.kt

@@ -1765,7 +1765,7 @@ class SyncServiceTest {
         }
 
     @Test
-    fun anIdenticalSyncSkipsTheArtistAggregateQuery() =
+    fun anIdenticalSyncSkipsTheAggregateQueries() =
         runTest {
             val context = ApplicationProvider.getApplicationContext<Context>()
             val executions = Collections.synchronizedList(mutableListOf<SqlExecution>())
@@ -1786,11 +1786,16 @@ class SyncServiceTest {
                     )
 
                 SyncService(loggingDb, source).sync()
+                val firstSyncExecutions = synchronized(executions) { executions.toList() }
+                assertTrue(firstSyncExecutions.any { it.sql.contains("credited_albums") })
+                assertTrue(firstSyncExecutions.any { it.sql.contains("UPDATE albums SET playCount") })
+
                 synchronized(executions) { executions.clear() }
                 SyncService(loggingDb, source).sync()
 
                 val secondSyncExecutions = synchronized(executions) { executions.toList() }
                 assertTrue(secondSyncExecutions.none { it.sql.contains("credited_albums") })
+                assertTrue(secondSyncExecutions.none { it.sql.contains("UPDATE albums SET playCount") })
             } finally {
                 loggingDb.close()
             }