HOLD current update (8-bit mode):
// Update HOLD on-the-fly: CFG_CH[31:24] = HFS (bit 7) | HOLD[6:0] (bits 6:0)
ChannelConfig config;
driver.GetChannelConfig(0, config);
uint8_t hold_raw = 60;  // 7-bit raw (0-127); or derive from config.hold_setpoint
driver.WriteRegister8(RegBank::CFG_CH0, (config.half_full_scale ? 0x80u : 0u) | (hold_raw & 0x7Fu));