fix(install): move empty-element cleanup to postflight, drop ALTER

The ALTER TABLE NOT NULL breaks Joomla's package installer on MySQL
strict mode. Instead, clean up empty-element rows and stale files in
postflight AFTER Joomla finishes installing sub-extensions.

source/script.php

@@ -46,45 +46,6 @@ class Pkg_MokosuiteclientInstallerScript
 	{
 		$this->saveDownloadKey();
 
-		// Remove DEFAULT '' from element column — a previous version set this
-		// which caused Joomla to install plugin files to the group root
-		try
-		{
-			$db = Factory::getDbo();
-			$db->setQuery("ALTER TABLE " . $db->quoteName('#__extensions')
-				. " MODIFY " . $db->quoteName('element') . " VARCHAR(100) NOT NULL");
-			$db->execute();
-
-			// Delete orphaned rows with empty element (created by the old DEFAULT '')
-			$db->setQuery("DELETE FROM " . $db->quoteName('#__extensions')
-				. " WHERE " . $db->quoteName('element') . " = ''");
-			$db->execute();
-			$deleted = $db->getAffectedRows();
-
-			if ($deleted > 0)
-			{
-				Log::add("Deleted {$deleted} orphaned extension row(s) with empty element", Log::INFO, 'mokosuiteclient');
-			}
-
-			// Remove stale plugin files that leaked to group root
-			$staleFiles = [
-				JPATH_PLUGINS . '/system/services',
-				JPATH_PLUGINS . '/system/src',
-				JPATH_PLUGINS . '/system/language',
-			];
-
-			foreach ($staleFiles as $stale)
-			{
-				if (is_dir($stale))
-				{
-					$this->rmdirRecursive($stale);
-				}
-			}
-		}
-		catch (\Throwable $e)
-		{
-			// Non-fatal
-		}
 	}
 
 	public function postflight($type, $parent)
@@ -136,6 +97,9 @@ class Pkg_MokosuiteclientInstallerScript
 		// Set up MokoSuiteClient guided tours and unpublish Joomla defaults
 		$this->setupGuidedTours();
 
+		// Clean up orphaned empty-element rows and stale files from old DEFAULT '' bug
+		$this->cleanupEmptyElements();
+
 		// Mark MokoSuiteClient extensions as protected (prevents disable/uninstall at framework level)
 		$this->protectExtensions();
 
@@ -543,6 +507,51 @@ class Pkg_MokosuiteclientInstallerScript
 	 *
 	 * @since   02.03.10
 	 */
+	private function cleanupEmptyElements(): void
+	{
+		try
+		{
+			$db = Factory::getDbo();
+
+			// Delete orphaned extension rows with empty element
+			$db->setQuery("DELETE FROM " . $db->quoteName('#__extensions')
+				. " WHERE " . $db->quoteName('element') . " = ''");
+			$db->execute();
+			$deleted = $db->getAffectedRows();
+
+			if ($deleted > 0)
+			{
+				Log::add("Deleted {$deleted} orphaned extension row(s) with empty element", Log::INFO, 'mokosuiteclient');
+				Factory::getApplication()->enqueueMessage(
+					sprintf('Cleaned up %d orphaned extension record(s).', $deleted),
+					'message'
+				);
+			}
+
+			// Remove stale plugin files that leaked to group root
+			foreach (['services', 'src', 'language'] as $dir)
+			{
+				$path = JPATH_PLUGINS . '/system/' . $dir;
+
+				if (is_dir($path))
+				{
+					$this->rmdirRecursive($path);
+					Log::add("Removed stale directory: plugins/system/{$dir}", Log::INFO, 'mokosuiteclient');
+				}
+			}
+
+			// Remove stale XML manifests at group root
+			foreach (glob(JPATH_PLUGINS . '/system/mokosuiteclient_*.xml') ?: [] as $staleXml)
+			{
+				@unlink($staleXml);
+			}
+		}
+		catch (\Throwable $e)
+		{
+			Log::add('Empty element cleanup error: ' . $e->getMessage(), Log::WARNING, 'mokosuiteclient');
+		}
+	}
+
 	private function protectExtensions(): void
 	{
 		try