Remove text truncation limits from Telegram posts

Posts were being cut to 300 chars (source ingestion) and 150 chars
(alert evaluation), losing valuable OSINT context. The sendMessage
chunker already handles the 4096-char Telegram API limit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/alerts/telegram.mjs

@@ -681,7 +681,7 @@ Respond with ONLY valid JSON:
     if (osintSignals.length > 0) {
       sections.push('📡 OSINT SIGNALS:\n' + osintSignals.map(s => {
         const post = s.item || s;
-        return `  [${post.channel || 'UNKNOWN'}] ${(post.text || s.reason || '').substring(0, 150)}`;
+        return `  [${post.channel || 'UNKNOWN'}] ${post.text || s.reason || ''}`;
       }).join('\n'));
     }