fix(qa): enforce critical-QA gate on export + fix neutral_background critical-but-passed (GAP-15/16, INV-QA3/EX3)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

mcp-server/src/legal_mcp/tools/drafting.py

@@ -399,6 +399,26 @@ async def export_docx(case_number: str, output_path: str = "") -> str:
 
     case_id = UUID(case["id"])
 
+    # INV-EX3 / INV-QA3: a decision cannot be exported while critical QA gates
+    # fail (or before QA has been run at all). Gate on the STORED qa_results —
+    # cheap SELECT, no LLM re-run.
+    if not await db.qa_run_exists(case_id):
+        return json.dumps({
+            "status": "error",
+            "message": "ייצוא נחסם: בקרת איכות (QA) טרם רצה על התיק. "
+                       "הרץ validate_decision לפני ייצוא.",
+        }, ensure_ascii=False, indent=2)
+
+    critical = await db.get_critical_qa_failures(case_id)
+    if critical:
+        gate_names = ", ".join(r["check_name"] for r in critical)
+        return json.dumps({
+            "status": "error",
+            "message": f"ייצוא נחסם: שערי QA קריטיים נכשלו ({gate_names}). "
+                       f"תקן את הליקויים והרץ validate_decision מחדש לפני ייצוא.",
+            "failed_gates": [r["check_name"] for r in critical],
+        }, ensure_ascii=False, indent=2)
+
     try:
         path = await docx_exporter.export_decision(case_id, output_path or None)
         # Register this export as the new source of truth