Escape Markdown in alert signals and cap OSINT text in ideas prompt

Addresses PR review: escape Markdown-sensitive characters in
_formatTieredAlert signal bullets to prevent Telegram Bot API
rejections, and add a 1500-char budget for URGENT_OSINT in
compactSweepForLLM to bound prompt size while keeping full text upstream.

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

lib/alerts/telegram.mjs

@@ -730,7 +730,7 @@ Respond with ONLY valid JSON:
     if (evaluation.signals?.length) {
       lines.push('', `*Signals:*`);
       for (const sig of evaluation.signals) {
-        lines.push(`• ${sig}`);
+        lines.push(`• ${escapeMd(sig)}`);
       }
     }
 
@@ -742,6 +742,11 @@ Respond with ONLY valid JSON:
 
 // ─── Helpers ──────────────────────────────────────────────────────────────
 
+function escapeMd(text) {
+  if (!text) return '';
+  return text.replace(/([_*\[\]()~`>#+\-=|{}.!\\])/g, '\\$1');
+}
+
 function parseJSON(text) {
   if (!text) return null;
   let cleaned = text.trim();

lib/llm/ideas.mjs

@@ -88,10 +88,20 @@ function compactSweepForLLM(data, delta, previousIdeas) {
     sections.push(`SUPPLY_CHAIN: GSCPI=${data.gscpi.value} (${data.gscpi.interpretation})`);
   }
 
-  // Geopolitical signals
+  // Geopolitical signals (cap total OSINT text to ~1500 chars to keep prompt compact)
   const urgentPosts = (data.tg?.urgent || []).slice(0, 5);
   if (urgentPosts.length) {
-    sections.push(`URGENT_OSINT:\n${urgentPosts.map(p => `- ${p.text || ''}`).join('\n')}`);
+    const MAX_OSINT_CHARS = 1500;
+    let remaining = MAX_OSINT_CHARS;
+    const lines = [];
+    for (const p of urgentPosts) {
+      const text = p.text || '';
+      if (remaining <= 0) break;
+      const trimmed = text.length > remaining ? text.substring(0, remaining) + '…' : text;
+      lines.push(`- ${trimmed}`);
+      remaining -= trimmed.length;
+    }
+    sections.push(`URGENT_OSINT:\n${lines.join('\n')}`);
   }
 
   // Thermal / fire detections