feat: add certificate ROUGE-N recall function used in summary scorecard

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

scripts/rouge_certificate_fn.py

@@ -0,0 +1,29 @@
+from __future__ import annotations
+
+import re
+from collections import Counter
+
+
+def ngram_tokenize(text: str, n: int = 2) -> list[tuple[str, ...]]:
+    """공백을 제거한 문자 단위 n-gram 목록"""
+    tokens = list(re.sub(r"\s+", "", text))
+    return [tuple(tokens[i:i + n]) for i in range(len(tokens) - n + 1)]
+
+
+def calculate_rouge_n(reference: str, hypothesis: str, n: int = 2) -> float:
+    """N-gram 기반 ROUGE 점수 계산 (계획서 p.24 수식: recall)"""
+    ref_ngrams = ngram_tokenize(reference, n)
+    hyp_ngrams = ngram_tokenize(hypothesis, n)
+
+    if not ref_ngrams or not hyp_ngrams:
+        return 0.0
+
+    ref_counter = Counter(ref_ngrams)
+    hyp_counter = Counter(hyp_ngrams)
+
+    overlap = 0
+    for ngram in hyp_counter:
+        overlap += min(hyp_counter[ngram], ref_counter.get(ngram, 0))
+
+    recall = overlap / len(ref_ngrams) if len(ref_ngrams) > 0 else 0
+    return recall