fix: Hard main template rendering lock

- Added $rendering_main_template flag that blocks all other renders
- Reduced MAX_RENDER_DEPTH from 5 to 2
- template-wrapper.php passes is_main_template=true to enable hard lock
- Any render attempt during main template rendering is blocked

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

wp-fedistream.php

@@ -26,7 +26,7 @@ if ( ! defined( 'ABSPATH' ) ) {
  *
  * @var string
  */
-define( 'WP_FEDISTREAM_VERSION', '0.4.6' );
+define( 'WP_FEDISTREAM_VERSION', '0.4.7' );
 
 /**
  * Plugin file path.