Function quant_mode_from_environment 

pub fn quant_mode_from_environment() -> QuantLinearMode

The armed quantized-linear mode for the talker/microdecoder route.

FTTS_INT8=1 or w8a8 selects the int8-dot route; FTTS_INT8=w8a16 selects the weight-only route. Anything else means the caller should not be arming quantization at all (the kill-switch check happens before this is consulted).