test: verify offline model failure message

backend/tests/test_llm_and_rag.py

@@ -6,7 +6,7 @@ from sqlalchemy import select
 
 from wisegrade.llm import DeepSeekClient, ModelError, ScoreResult, validate_score
 from wisegrade.models import AppSetting, KnowledgeChunk
-from wisegrade.rag import ingest, retrieve, split_pages
+from wisegrade.rag import ingest, local_encoder, retrieve, split_pages
 from wisegrade.settings_store import model_config, save_model_config
 
 
@@ -63,3 +63,8 @@ def test_model_key_is_encrypted_and_hidden(db):
     stored = db.get(AppSetting, "api_key")
     assert b"test-private-key" not in stored.encrypted_value
     assert model_config(db)["model"] == "deepseek-flash"
+
+
+def test_missing_offline_embedding_package_fails_clearly(tmp_path):
+    with pytest.raises(RuntimeError, match="离线嵌入模型不存在"):
+        local_encoder(str(tmp_path / "missing-model"))