b24ac6883f
wrap_plugin_route copied __signature__ from the original handler but
the wrapper's __globals__ namespace (plugin_error_handler.py) did not
contain the Pydantic models (ConversationCreate, MessageCreate, etc.).
FastAPI could not resolve ForwardRef('ConversationCreate') → 422 on
all POST routes with body parameters.
Removing the wrapper entirely fixes this. Plugin error isolation can
be re-added later using a different approach (middleware or exception handler).