fix: set reasoning_effort=none when tools present for OpenAI reasoning models

internal/providers/helpers.go

@@ -191,6 +191,7 @@ func BuildOpenAIBody(request *models.UnifiedRequest, messagesJSON []interface{},
 			}
 		}
 		body["tools"] = sanitizedTools
+		body["reasoning_effort"] = "none" // pontytail: OpenAI reasoning models reject tools + reasoning_effort
 	}
 	if request.ToolChoice != nil {
 		var toolChoice interface{}