feat: add conversational Telegram AI chat

apis/sources/telegram.mjs

@@ -109,14 +109,18 @@ async function fetchBotUpdates() {
     return { error: result?.description || 'Bot API request failed' };
   }
 
-  const messages = result.result
-    .map(u => u.message || u.channel_post || u.edited_channel_post)
-    .filter(Boolean)
-    .map(compactBotMessage);
+  const messages = extractBotChannelMessages(result.result);
 
   return { messages, count: messages.length };
 }
 
+export function extractBotChannelMessages(updates = []) {
+  return updates
+    .map(update => update.channel_post || update.edited_channel_post)
+    .filter(Boolean)
+    .map(compactBotMessage);
+}
+
 // ─── Web preview scraping fallback ──────────────────────────────────────────
 
 // Fetch raw HTML from a URL (safeFetch truncates non-JSON to 500 chars, too short)