Remove DB_NAME fallback for the legacy driver

The filter-based fallback to 'database_name_here' was added to ease early
adoption of the new AST-based driver in projects that didn't define DB_NAME.
With the legacy driver removed, simplify to a plain ternary — matching how
WPDB itself handles the constant.

Author: JanJakes

packages/plugin-sqlite-database-integration/wp-includes/sqlite/db.php

@@ -51,20 +51,7 @@
 require_once __DIR__ . '/class-wp-sqlite-db.php';
 require_once __DIR__ . '/install-functions.php';
 
-/**
- * The DB_NAME constant is required by the new SQLite driver.
- *
- * There are some existing projects in which the DB_NAME constant is missing in
- * wp-config.php. To enable easier early adoption and testing of the new SQLite
- * driver, let's allow using a default database name when DB_NAME is not set.
- *
- * TODO: For version 3.0, enforce the DB_NAME constant and remove the fallback.
- */
-if ( defined( 'DB_NAME' ) && '' !== DB_NAME ) {
-	$db_name = DB_NAME;
-} else {
-	$db_name = apply_filters( 'wp_sqlite_default_db_name', 'database_name_here' );
-}
+$db_name = defined( 'DB_NAME' ) ? DB_NAME : '';
 
 /*
  * Debug: Cross-check with MySQL.