test: 覆盖率提升至 100%（fail_under 90→99，13 个防御/边界用例）

tests/test_config.py

@@ -48,4 +48,14 @@ def test_env_placeholder_expansion(monkeypatch):
 def test_redacted_hides_secrets():
     s = Settings.from_dir(FIXTURES)
     red = s.get_redacted()
-    assert red["rag"]["vector_store"]["qdrant"]["api_key"] == "***"
+    assert red["rag"]["vector_store"]["qdrant"]["api_key"] == "***"
+
+
+def test_expand_env_list_branch(monkeypatch):
+    # _expand_env 的 list 分支（L134）：列表项递归展开环境占位
+    from genesis.config import _expand_env
+    monkeypatch.setenv("QDRANT_API_KEY", "sk-list-xyz")
+    data = {"models": [{"name": "a", "key": "${QDRANT_API_KEY}"}, "plain"]}
+    out = _expand_env(data)
+    assert out["models"][0]["key"] == "sk-list-xyz"
+    assert out["models"][1] == "plain"