feat(search): ASME 절-KB schema 379 + doc_kind retrieval 필터

- migration 379: documents +parent_id/doc_kind/clause_code/clause_part/clause_order + clause_links/document_tags
- _license_sql 에 doc_kind=standard 필터(절-문서 read/nav 전용, 검색 제외; 전 문서 standard=동작보존)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/services/search/retrieval_service.py

@@ -142,7 +142,9 @@ def _license_sql(alias: str) -> str:
     술어 정의 = license_filter.restricted_exclude_sql 공유(digest/briefing/study 풀이와 단일 source).
     """
     from services.search.license_filter import restricted_exclude_sql
-    return " AND " + restricted_exclude_sql(alias)
+    _p = (alias + ".") if alias else ""
+    # ASME clause-KB(379): clause docs (doc_kind='clause') = read/nav/backlink only, excluded from retrieval/digest legs.
+    return " AND " + restricted_exclude_sql(alias) + f" AND {_p}doc_kind = 'standard'"
 
 
 def cloud_eligible_doc_sql(alias: str = "") -> str: