Wire MediaEmbedExtension into Document::renderMarkdown

The extension registers a DocumentParsedEvent listener that walks the
AST, finds Image nodes whose URLs match media patterns (via
MediaUrlResolver), and replaces them with MediaEmbedNode instances
containing the appropriate <video>/<audio>/<iframe> markup.

A custom MediaEmbedNode + MediaEmbedNodeRenderer pair bypasses the
html_input filter (which would strip raw HTML when set to 'strip'),
allowing programmatically generated embed HTML to pass through safely
while user-authored raw HTML remains stripped.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/Models/Document.php

@@ -127,6 +127,7 @@ public static function renderMarkdown(string $markdown): string
         ]);
 
         $converter->getEnvironment()->addExtension(new GithubFlavoredMarkdownExtension());
+        $converter->getEnvironment()->addExtension(new \App\Markdown\MediaEmbedExtension());
 
         return $converter->convert($markdown)->getContent();
     }