fix(grounding): citation marker [n] 을 fabricated_number 에서 제외

[1][2][4] 같은 citation 마커의 숫자가 evidence 에 없다고 판정되어
모든 정상 답변이 refuse(2+strong) 되는 critical bug.
answer 에서 \[\d+\] 제거 후 숫자 추출.

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

app/services/search/grounding_check.py

@@ -76,14 +76,16 @@ def check(
 
     evidence_text = " ".join(e.span_text for e in evidence)
 
-    # ── Strong 1: fabricated number ──
-    answer_nums = _extract_number_literals(answer)
+    # ── Strong 1: fabricated number (equality, not substring) ──
+    # ⚠ citation marker [n] 제거 후 숫자 추출 (안 그러면 [1][2][3] 이 fabricated 로 오탐)
+    answer_clean = re.sub(r'\[\d+\]', '', answer)
+    answer_nums = _extract_number_literals(answer_clean)
     evidence_nums = _extract_number_literals(evidence_text)
+    evidence_digits = {re.sub(r'[^\d]', '', en) for en in evidence_nums}
+    evidence_digits.discard('')
     for num in answer_nums:
         digits_only = re.sub(r'[^\d]', '', num)
-        if digits_only and not any(
-            digits_only in re.sub(r'[^\d]', '', en) for en in evidence_nums
-        ):
+        if digits_only and digits_only not in evidence_digits:
             strong.append(f"fabricated_number:{num}")
 
     # ── Strong/Weak 2: query-answer intent alignment ──