debug: add logging and debug endpoint to article-og

Add console logging for debugging and ?debug=1 query param to see request details in browser.

api/article-og.ts

@@ -213,10 +213,27 @@ export default async function handler(req: VercelRequest, res: VercelResponse) {
   }
 
   const userAgent = req.headers['user-agent'] as string | undefined
+  const isCrawlerRequest = isCrawler(userAgent)
+
+  const debugInfo = {
+    naddr: naddr.slice(0, 20) + '...',
+    userAgent: userAgent?.slice(0, 80),
+    isCrawler: isCrawlerRequest,
+    url: req.url,
+    referer: req.headers.referer,
+    accept: req.headers.accept
+  }
+
+  console.log('[article-og]', debugInfo)
+
+  // Debug mode: if ?debug=1, return JSON
+  if (req.query.debug === '1') {
+    return res.status(200).json(debugInfo)
+  }
 
   // If it's a regular browser (not a bot), serve index.html with base tag
   // The rewrite preserves the URL, so SPA routing will handle /a/{naddr}
-  if (!isCrawler(userAgent)) {
+  if (!isCrawlerRequest) {
     const fs = await import('fs')
     const path = await import('path')
     // eslint-disable-next-line no-undef