fix(installer): verify install success before showing success

Gate the success/license path in both installer scripts so a partial
install can no longer report success.

- Package script (pkg_mokosuitecross): add missingChildExtensions(),
  which reads the package manifest via getParent()->getManifest() and
  verifies each declared <file> child is registered in #__extensions
  (matching element+type, plus folder=group for plugins). If any are
  missing, enqueue an error and return before warnMissingLicenseKey().
  Housekeeping (download-key restore, core-plugin enable, PerfectPublisher
  migration detection) still runs unconditionally.
- Component script (com_mokosuitecross): postflight was empty. Add
  missingTables(), which parses the installed sql/install.mysql.sql for
  every CREATE TABLE and verifies each exists (prefix-substituted,
  case-insensitive). On any missing tables, enqueue an error and return
  before the success message; otherwise show install-success/license notice.

Both checks fail open (try/catch returning []/true) so a glitch never turns
a good install into a false failure. Extension names are htmlspecialchars'd.

Claude-Session: https://claude.ai/code/session_01MrxXW9iyuDda5yDZrjZMbF

source/script.php

@@ -40,8 +40,8 @@ class Pkg_MokoSuiteCrossInstallerScript
 
 	public function postflight(string $type, InstallerAdapter $parent): void
 	{
+		// The download key must be restored regardless of the install outcome.
 		$this->restoreDownloadKey();
-		$this->warnMissingLicenseKey();
 
 		$db = Factory::getDbo();
 
@@ -76,6 +76,97 @@ class Pkg_MokoSuiteCrossInstallerScript
 
 			$this->detectPerfectPublisherPro($db);
 		}
+
+		// Be smart: only run the success path (and show the licence notice, which
+		// implies a completed install) when every child extension declared in the
+		// package manifest actually registered. If any are missing, the package
+		// did NOT install successfully — surface that instead of implying success.
+		$missing = $this->missingChildExtensions($parent);
+
+		if ($missing !== [])
+		{
+			Factory::getApplication()->enqueueMessage(
+				'<strong>MokoSuiteCross did not install completely.</strong> '
+				. 'The following extension(s) failed to install: '
+				. htmlspecialchars(implode(', ', $missing), ENT_QUOTES, 'UTF-8') . '. '
+				. 'Resolve the errors shown above, then uninstall and reinstall the package.',
+				'error'
+			);
+
+			return;
+		}
+
+		$this->warnMissingLicenseKey();
+	}
+
+	/**
+	 * Compare the child extensions the package manifest declares against what is
+	 * actually registered in #__extensions after the install/update. Returns the
+	 * label of each declared extension that is missing (i.e. failed to install);
+	 * an empty array means every child installed and the package succeeded.
+	 *
+	 * Fails open: any error returns [] so a query problem can never turn a good
+	 * install into a false "did not install completely" warning.
+	 *
+	 * @param   InstallerAdapter  $parent
+	 * @return  string[]
+	 */
+	private function missingChildExtensions(InstallerAdapter $parent): array
+	{
+		$missing = [];
+
+		try
+		{
+			$manifest = $parent->getParent()->getManifest();
+
+			if (!$manifest || !isset($manifest->files) || !isset($manifest->files->file))
+			{
+				return [];
+			}
+
+			$db = Factory::getDbo();
+
+			foreach ($manifest->files->file as $file)
+			{
+				$type    = (string) $file['type'];
+				$element = (string) $file['id'];
+				$group   = (string) $file['group'];
+
+				if ($element === '')
+				{
+					continue;
+				}
+
+				$query = $db->getQuery(true)
+					->select('COUNT(*)')
+					->from($db->quoteName('#__extensions'))
+					->where($db->quoteName('element') . ' = ' . $db->quote($element));
+
+				if ($type !== '')
+				{
+					$query->where($db->quoteName('type') . ' = ' . $db->quote($type));
+				}
+
+				// Plugins are only unique by element + folder (the manifest "group").
+				if ($type === 'plugin' && $group !== '')
+				{
+					$query->where($db->quoteName('folder') . ' = ' . $db->quote($group));
+				}
+
+				$db->setQuery($query);
+
+				if ((int) $db->loadResult() === 0)
+				{
+					$missing[] = $element . ($group !== '' ? ' (' . $group . ')' : '');
+				}
+			}
+		}
+		catch (\Throwable $e)
+		{
+			return [];
+		}
+
+		return $missing;
 	}
 
 	private function detectPerfectPublisherPro($db): void