fix: default gain to 0 instead of brightness per protocol examples

miniprogram/services/ble/protocol.js

@@ -172,7 +172,7 @@ function buildVendorCommand(options) {
   var regionMask = options.region_mask || REGION.FULL_FACE
   var wavelength = options.wavelength || WAVELENGTH.R
   var brightness = clampByte(options.brightness === undefined ? 200 : options.brightness)
-  var gain = clampUInt16(options.current_gain === undefined ? brightness : options.current_gain)
+  var gain = clampUInt16(options.current_gain === undefined ? 0 : options.current_gain)
   var durationMs = options.duration_ms || 600000
   var holdSeconds = clampUInt16(options.hold_time === undefined ? Math.round(durationMs / 1000) : options.hold_time)
   var control = options.control !== undefined ? options.control : CONTROL.TREAT