fix(security): no direct HTTP access to plugin PHP files (audit L2, cheap part)

Every file under src/ exits outside WordPress (defined('ABSPATH') ||
exit; after the use block, so a direct request no longer prints a fatal
error with the server path); divi-convert-fixture.php gets the WP_CLI
guard the other integration scripts have. A unit test keeps both true;
PSR1 side-effects warning excluded for the guard.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

src/Integrations/Divi/Pages/DiviComposition.php

@@ -18,6 +18,8 @@ use LIT\MCP\Integrations\Divi\Compose\Warnings;
 use LIT\MCP\Integrations\Divi\Design\DesignSystemReader;
 use LIT\MCP\Integrations\Divi\Schema\DiviModules;
 
+defined('ABSPATH') || exit;
+
 /**
  * Wires the pure Compose classes with the live catalog, design system, Divi's dynamic content
  * registry and the WordPress sanitizer/media lookup – once per request and entry. Ruling S31: