Adds a Select entity with four options (Normal / Charge Disabled /
Discharge Disabled / Both Disabled) that sends the 0xE1 write command
to the BMS and immediately refreshes sensor state. Current option is
derived from the mos_charge_enabled / mos_discharge_enabled bits
already parsed on every poll.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
