LCORE-1426: fix test and linter issues from review feedback

- Replace assert with runtime ValueError for bandit compliance
- Fix backend="rag" → backend="faiss" in test helper
- Add pylint disable for no-member on Pydantic model validator

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: are-ces

src/llama_stack_configuration.py

@@ -22,10 +22,11 @@
     # "pgvector": "remote::pgvector",  # TODO(are-ces): add enrichment support
 }
 
-assert constants.DEFAULT_RAG_BACKEND in BACKEND_TO_LLAMA_STACK_PROVIDER, (
-    f"DEFAULT_RAG_BACKEND '{constants.DEFAULT_RAG_BACKEND}' has no entry in "
-    f"BACKEND_TO_LLAMA_STACK_PROVIDER — add a mapping before changing the default."
-)
+if constants.DEFAULT_RAG_BACKEND not in BACKEND_TO_LLAMA_STACK_PROVIDER:
+    raise ValueError(
+        f"DEFAULT_RAG_BACKEND '{constants.DEFAULT_RAG_BACKEND}' has no entry in "
+        f"BACKEND_TO_LLAMA_STACK_PROVIDER — add a mapping before changing the default."
+    )
 
 
 class YamlDumper(yaml.Dumper):  # pylint: disable=too-many-ancestors

src/models/config.py

@@ -2066,6 +2066,7 @@ class RagConfiguration(ConfigurationBase):
     @model_validator(mode="after")
     def validate_retrieval_sources(self) -> Self:
         """Reject retrieval source IDs not declared in byok.stores or OKP."""
+        # pylint: disable=no-member
         known_ids = {store.rag_id for store in self.byok.stores}
         known_ids.add(constants.OKP_RAG_ID)
 

tests/unit/utils/test_responses.py

@@ -1712,7 +1712,7 @@ def _make_byok_rag(rag_id: str, vector_db_id: str) -> RagStore:
             rag_id=rag_id,
             vector_db_id=vector_db_id,
             db_path="tests/configuration/rag.txt",
-            backend="rag",
+            backend="faiss",
             embedding_model="model",
             embedding_dimension=768,
             score_multiplier=1.0,