Fix fresh checkout test failures

Make .env optional in tests and prevent endpoint resolver stubs from leaking into model route tests.

tests/test_model_routes.py

@@ -6,6 +6,13 @@ from unittest.mock import MagicMock
 import httpx
 import pytest
 
+_endpoint_resolver = sys.modules.get("src.endpoint_resolver")
+if _endpoint_resolver is not None and not getattr(_endpoint_resolver, "__file__", None):
+    # Other tests stub this module during collection. These helper tests need
+    # the real URL normalization helpers so Anthropic /v1 handling is covered.
+    sys.modules.pop("src.endpoint_resolver", None)
+    sys.modules.pop("routes.model_routes", None)
+
 if "core.database" not in sys.modules:
     _core_db = types.ModuleType("core.database")
     for _name in [