fix: OCR fidelity scoring reform — prevent false fail from language-mismatched field names

Root cause (from review): field_coverage compared English JRXML field names
against Chinese OCR field names with set intersection — always zero. Combined
with 0.5 weight in score formula, caused valid JRXML (XSD pass, 82% element
coverage) to score 0.41 < 0.5 → fail → correction loop → progressive destruction.

Changes:
- Scoring weight: element_coverage 0.8 + field_coverage 0.2 (was 0.5+0.5)
- Validate node: only fail on fidelity when BOTH score<0.5 AND element_coverage<0.4
- Field name regex: \w+ → [^"]+ to support non-ASCII field names
- Field matching: also try _sanitize_field_name conversion (Chinese→_uXXXX_)
- correction.md: namespace check always active, not conditional on error keywords

agent/nodes.py

@@ -1207,8 +1207,8 @@ def _check_ocr_fidelity(jrxml: str, state: dict) -> dict:
     else:
         element_coverage = 1.0
 
-    # 2. 字段名覆盖
-    jrxml_fields = set(re.findall(r'<field name="(\w+)"', jrxml))
+    # 2. 字段名覆盖（英文字段名 vs OCR 中文字段名天然不匹配，权重降低）
+    jrxml_fields = set(re.findall(r'<field name="([^"]+)"', jrxml))
     ocr_field_names = set()
     ocr_fields = ocr_result.get("fields", []) if isinstance(ocr_result, dict) else []
     for f in ocr_fields:
@@ -1219,10 +1219,15 @@ def _check_ocr_fidelity(jrxml: str, state: dict) -> dict:
 
     if ocr_field_names and jrxml_fields:
         matched = jrxml_fields & ocr_field_names
-        field_coverage = len(matched) / max(len(ocr_field_names), 1)
-        unmatched = ocr_field_names - jrxml_fields
-        if unmatched:
-            sample = list(unmatched)[:8]
+        # 尝试通过 _sanitize_field_name 转义后匹配（中文→_uXXXX_）
+        sanitized_ocr = {_sanitize_field_name(n) for n in ocr_field_names}
+        matched_via_sanitize = jrxml_fields & sanitized_ocr
+        all_matched = matched | matched_via_sanitize
+        field_coverage = len(all_matched) / max(len(ocr_field_names), 1)
+        still_unmatched = {n for n in ocr_field_names
+                           if n not in jrxml_fields and _sanitize_field_name(n) not in jrxml_fields}
+        if still_unmatched:
+            sample = list(still_unmatched)[:8]
             issues.append(f"OCR 字段未在 JRXML 中声明: {', '.join(sample)}")
     elif ocr_field_names and not jrxml_fields:
         field_coverage = 0.0
@@ -1247,8 +1252,9 @@ def _check_ocr_fidelity(jrxml: str, state: dict) -> dict:
                     f"OCR 布局分析有 {ocr_columns} 列"
                 )
 
-    # 综合评分
-    score = round(field_coverage * 0.5 + element_coverage * 0.5, 3)
+    # 综合评分（元素覆盖为主权重 0.8，字段覆盖为辅助 0.2）
+    # 英文字段名 vs 中文 OCR 字段名天然不匹配是预期行为，字段覆盖仅作参考
+    score = round(element_coverage * 0.8 + field_coverage * 0.2, 3)
     return {
         "score": score,
         "field_coverage": round(field_coverage, 3),
@@ -1291,7 +1297,8 @@ def validate(state: AgentState) -> Dict:
     if fidelity["issues"]:
         if state["status"] == "pass":
             # XSD 通过但内容保真度不足 → 降级为 fail
-            if fidelity["score"] < 0.5:
+            # 需要 score < 0.5 且 element_coverage < 0.4（字段名语言不匹配不应单独导致 fail）
+            if fidelity["score"] < 0.5 and fidelity.get("element_coverage", 0) < 0.4:
                 state["status"] = "fail"
                 state["error_msg"] = (
                     f"[内容保真度不足] 得分 {fidelity['score']:.2f}/1.0。"