Home Assistant auto mode is described as
"The device is set to a schedule, learned behavior, AI."
HomeKit Accessory Protocol expects "heating or cooling to maintain
temperature within the heating and cooling threshold of the
target temperature"
Since HomeKit is expecting to set temperatures in this mode,
mapping homekit state 3 ("Auto") to Home Assistant HVAC_MODE_HEAT_COOL
is more inline with how Home Assistant defines HVAC_MODE_HEAT_COOL
as "The device supports heating/cooling to a range"
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