test(auxiliary): update _resolve_auto patch to _resolve_auto_route

The PR renamed _resolve_auto to _resolve_auto_route (3-tuple return).
This test patches the resolver to mock the auto-detection chain, but was
still patching the old _resolve_auto name. The patch never fired, so the
test fell through to the real auto-detection (which finds no providers
in CI's hermetic env). Update patch target to _resolve_auto_route with
the 3-tuple return value.

tests/agent/test_auxiliary_main_first.py

@@ -126,8 +126,8 @@ class TestResolveAutoMainFirst:
             "agent.auxiliary_client._read_main_model",
             return_value="claude-opus-4-8",
         ) as mock_read_main_model, patch(
-            "agent.auxiliary_client._resolve_auto",
-            return_value=(runtime_client, "gpt-5.5"),
+            "agent.auxiliary_client._resolve_auto_route",
+            return_value=(runtime_client, "gpt-5.5", "openai-codex"),
         ) as mock_resolve_auto:
             from agent.auxiliary_client import resolve_provider_client