[nanomad]

Closes #35. Part of #26.

Adds control_ventilated_seat(vin, *, seat: VentilatedSeat, level: int), which sets one ventilated seat per command, front or rear. It mirrors control_heated_seat.

What it sends

• rvcReqType 22 (new RvcReqType.VENTILATED_SEATS).
• A single parameter for the chosen seat, then the end-of-parameters marker (255, value 0):

Seat	Parameter
VentilatedSeat.FRONT_LEFT	27
VentilatedSeat.FRONT_RIGHT	28
VentilatedSeat.REAR_LEFT	29
VentilatedSeat.REAR_RIGHT	30

• Levels: 0 is off. Seats with several levels take 1, 2 or 3. Seats with a single level take ONE_LEVEL_VENTILATED_SEAT_ON_LEVEL (3) for on. Levels outside 0-3 raise ValueError.
• Status: BasicVehicleStatus gains frontLeftSeatVentLevel, frontRightSeatVentLevel, secondRowLeftSeatVentLevel and secondRowRightSeatVentLevel. They default to None, so cars without ventilated seats are unaffected.
• Sides: left and right are physical sides, as for the heated seats.

Draft: not tested on a car

The values come from static analysis of the iSmart app, not from a capture. This PR has not been checked on a car. Things only a car can settle:

• Whether the car accepts these values, and whether levels 1 and 2 differ on multi-level seats.
• Whether the car needs the trailing 255, and whether an omitted seat is held or cleared.
• Whether heat and ventilation exclude each other on the same seat. The commands don't couple them.
• Which cars offer front or rear ventilated seats. The client doesn't check capabilities, so callers should.

Please test on a car with ventilated seats (the issue reporter's MG S6?) before this is marked ready.

Changes

• api/vehicle/schema.py: four RvcParamsId values, RvcReqType.VENTILATED_SEATS and four status fields
• api/vehicle/climate/schema.py: VentilatedSeat and ONE_LEVEL_VENTILATED_SEAT_ON_LEVEL
• api/vehicle/climate/__init__.py: control_ventilated_seat()
• tests/test_ventilated_seats.py: every seat and level byte for byte, the one-level on value, the range check and the status parsing
• README.md: feature list line

ruff, mypy and pytest pass locally on Python 3.13.

https://claude.ai/code/session_013xKSpu8ev4cxQNsitcCidm