feat: add local LLMWiki wiki vector index

.gitignore

@@ -95,6 +95,12 @@ offline-backend-20260512/backend/tests/*
 !offline-backend-20260512/backend/tests/test_model_management.py
 # Keep fixed-question exact-match and streaming regression coverage versioned.
 !offline-backend-20260512/backend/tests/test_fixed_questions.py
+# Keep the local LLMWiki vector-index and external API regression coverage versioned.
+!offline-backend-20260512/backend/tests/test_llmwiki_local_index_repository.py
+!offline-backend-20260512/backend/tests/test_llmwiki_vector_search.py
+!offline-backend-20260512/backend/tests/test_llmwiki_wiki_sync.py
+!offline-backend-20260512/backend/tests/test_external_llmwiki_search.py
+!offline-backend-20260512/backend/tests/test_llmwiki_wiki_retrieval.py
 deploy
 .history