fix ty type check errors for real this time

use getattr() for name-mangled private method access instead of direct
attribute access, and use ty's native error code [unresolved-attribute]
instead of mypy's [union-attr] for .func suppression comments

Author: apkostka

backend/tests/test_langchain_chat_manager.py

@@ -95,15 +95,13 @@ def test_streaming_empty_chunk_skipped(mock_create_agent, oregon_state):
 
 def test_agent_creation_with_thread_id(oregon_state, portland_city):
     cm = LangChainChatManager()
-    agent = cm._LangChainChatManager__create_agent_for_session(  # type: ignore[attr-defined]
-        portland_city, oregon_state, "test-thread"
-    )
+    create = getattr(cm, "_LangChainChatManager__create_agent_for_session")
+    agent = create(portland_city, oregon_state, "test-thread")
     assert agent is not None
 
 
 def test_agent_creation_without_thread_id(oregon_state, portland_city):
     cm = LangChainChatManager()
-    agent = cm._LangChainChatManager__create_agent_for_session(  # type: ignore[attr-defined]
-        portland_city, oregon_state, None
-    )
+    create = getattr(cm, "_LangChainChatManager__create_agent_for_session")
+    agent = create(portland_city, oregon_state, None)
     assert agent is not None

backend/tests/test_langchain_tools.py

@@ -131,7 +131,7 @@ def test_retrieve_city_state_laws_returns_joined_docs(mock_rag_class):
     """Test that RAG results are joined with newlines."""
     mock_rag_class.return_value.search.return_value = "Doc1 content\nDoc2 content"
 
-    result = retrieve_city_state_laws.func(  # type: ignore[union-attr]
+    result = retrieve_city_state_laws.func(  # type: ignore[unresolved-attribute]
         query="eviction notice",
         state=UsaState("or"),
         city=OregonCity("portland"),
@@ -146,7 +146,7 @@ def test_retrieve_city_state_laws_empty_results(mock_rag_class):
     """Test behavior when RAG returns no documents."""
     mock_rag_class.return_value.search.return_value = ""
 
-    result = retrieve_city_state_laws.func(  # type: ignore[union-attr]
+    result = retrieve_city_state_laws.func(  # type: ignore[unresolved-attribute]
         query="obscure law",
         state=UsaState("or"),
         runtime=MagicMock(),
@@ -174,6 +174,6 @@ def test_generate_letter_empty_string(mock_get_stream_writer):
     mock_writer = MagicMock()
     mock_get_stream_writer.return_value = mock_writer
 
-    result = generate_letter.func(letter="")  # type: ignore[union-attr]
+    result = generate_letter.func(letter="")  # type: ignore[unresolved-attribute]
     mock_writer.assert_called_once_with({"type": "letter", "content": ""})
     assert result == "Letter generated successfully."