fix: flush PSR-4 autoload cache after install for Joomla 6 compat

Joomla 6 replaced the namespace column with a file-based autoload
cache. Package installs can regenerate it before all sub-extensions
are extracted, causing class-not-found errors (e.g. DB-IP plugin).
Deleting the cache in postflight forces a clean rebuild.

source/script.php

@@ -122,6 +122,9 @@ class Pkg_MokosuiteclientInstallerScript
 		// Restore download key saved in preflight
 		$this->restoreDownloadKey();
 
+		// Flush PSR-4 autoload cache so Joomla 6+ picks up new/updated namespaces
+		$this->flushAutoloadCache();
+
 		// Trigger heartbeat registration
 		$this->sendHeartbeat();
 
@@ -1077,6 +1080,23 @@ class Pkg_MokosuiteclientInstallerScript
 		}
 	}
 
+	/**
+	 * Delete the cached PSR-4 autoload map so Joomla rebuilds it from manifests.
+	 *
+	 * Joomla 6 replaced the #__extensions.namespace column with a file-based
+	 * cache. Package installs sometimes regenerate it before all sub-extensions
+	 * are extracted, leaving stale entries that cause class-not-found errors.
+	 */
+	private function flushAutoloadCache(): void
+	{
+		$cachePath = JPATH_ADMINISTRATOR . '/cache/autoload_psr4.php';
+
+		if (is_file($cachePath))
+		{
+			@unlink($cachePath);
+		}
+	}
+
 	/**
 	 * Send heartbeat to the MokoSuiteClient monitoring receiver.
 	 *