Fan wiring no switch, only using humidity sensor for control
You really need to add the switches as the instructions say to do. All warranties as well as any UL listings will be voided if not installed according to the directions. From a practical sense, you need a easy means to shut off the fan for cleaning and maintenance. It appears that only the brown wire needs to be connected to hot to do what you want but there's not a diagram of the sensor. Again, this is not recommended, follow the directions.