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>

migrations/379_asme_clause_kb.sql

@@ -0,0 +1,37 @@
+-- 379_asme_clause_kb.sql
+-- ASME 절-지식베이스: 절 = 개별 documents 행(parent_id) + 절↔절 백링크 + 태깅 (additive, idempotent)
+-- 검색 무접촉: 절 doc 은 embedding NULL(벡터 제외) + doc_kind='clause'(retrieval doc-leg 필터로 제외).
+
+ALTER TABLE documents
+  ADD COLUMN IF NOT EXISTS parent_id    bigint REFERENCES documents(id),
+  ADD COLUMN IF NOT EXISTS doc_kind     text NOT NULL DEFAULT 'standard',
+  ADD COLUMN IF NOT EXISTS clause_code  text,
+  ADD COLUMN IF NOT EXISTS clause_part  text,
+  ADD COLUMN IF NOT EXISTS clause_order int;
+
+CREATE INDEX IF NOT EXISTS idx_documents_parent_id   ON documents(parent_id) WHERE parent_id IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_documents_doc_kind    ON documents(doc_kind);
+CREATE INDEX IF NOT EXISTS idx_documents_clause_code ON documents(clause_code) WHERE clause_code IS NOT NULL;
+
+-- 절↔절 백링크 (dangling 허용: dst_doc_id nullable)
+CREATE TABLE IF NOT EXISTS clause_links (
+  id          bigserial PRIMARY KEY,
+  src_doc_id  bigint NOT NULL REFERENCES documents(id) ON DELETE CASCADE,
+  dst_code    text   NOT NULL,
+  dst_doc_id  bigint REFERENCES documents(id) ON DELETE SET NULL,
+  anchor      text,
+  ctx         text,
+  char_off    int
+);
+CREATE INDEX IF NOT EXISTS idx_clause_links_src     ON clause_links(src_doc_id);
+CREATE INDEX IF NOT EXISTS idx_clause_links_dst     ON clause_links(dst_doc_id) WHERE dst_doc_id IS NOT NULL;
+CREATE INDEX IF NOT EXISTS idx_clause_links_dstcode ON clause_links(dst_code);
+
+-- 태깅 (Part 자동 + 주제)
+CREATE TABLE IF NOT EXISTS document_tags (
+  doc_id    bigint NOT NULL REFERENCES documents(id) ON DELETE CASCADE,
+  tag       text   NOT NULL,
+  tag_kind  text   NOT NULL DEFAULT 'topic',
+  PRIMARY KEY (doc_id, tag)
+);
+CREATE INDEX IF NOT EXISTS idx_document_tags_tag ON document_tags(tag);