test: stabilize full test collection

tests/test_chat_image_routing.py

@@ -1,6 +1,13 @@
 import json
+import sys
 from types import SimpleNamespace
 
+_endpoint_resolver = sys.modules.get("src.endpoint_resolver")
+if _endpoint_resolver is not None and not getattr(_endpoint_resolver, "__file__", None):
+    sys.modules.pop("src.endpoint_resolver", None)
+    sys.modules.pop("routes.model_routes", None)
+    sys.modules.pop("routes.chat_routes", None)
+
 from routes import chat_routes