Auto dark/bright takes a light sensor where the device allows one

lib/theme/light.dart: dark at 15 lux or less, bright from 60, held 5 s; Settings shows the
reading. The Redmi Pad SE refuses apps its only light sensor (Xiaomi's, from the front
camera), so there Auto keeps following Android's dark theme. DASH-NEXT.md records the
other lux sources.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/app/src/main/kotlin/dev/yukart/display/MainActivity.kt

@@ -2,6 +2,10 @@ package dev.yukart.display
 
 import android.content.Context
 import android.content.Intent
+import android.hardware.Sensor
+import android.hardware.SensorEvent
+import android.hardware.SensorEventListener
+import android.hardware.SensorManager
 import android.net.ConnectivityManager
 import android.net.Network
 import android.net.NetworkCapabilities
@@ -10,6 +14,7 @@ import android.os.Bundle
 import android.view.WindowManager
 import io.flutter.embedding.android.FlutterActivity
 import io.flutter.embedding.engine.FlutterEngine
+import io.flutter.plugin.common.EventChannel
 import io.flutter.plugin.common.MethodChannel
 
 /**
@@ -22,6 +27,9 @@ import io.flutter.plugin.common.MethodChannel
  *   When asked, the whole process is bound to the Ethernet (NCM) network while it
  *   exists, and unbound when it goes.
  *
+ * Also the light sensor, for auto dark/bright (lib/theme/light.dart): lux on `yukart/light`
+ * while Dart listens, where the device lets apps read one (the Redmi Pad SE does not).
+ *
  * Also a development hook: `am start -n dev.yukart.display/.MainActivity --es linktest [dl:|bi:]<label>[@<host>]`
  * runs the link test (lib/linktest.dart) without touching the screen.
  */
@@ -81,6 +89,34 @@ class MainActivity : FlutterActivity() {
             .removeCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
             .build()
         cm.requestNetwork(request, callback)
+
+        EventChannel(flutterEngine.dartExecutor.binaryMessenger, "yukart/light")
+            .setStreamHandler(LightStream(getSystemService(Context.SENSOR_SERVICE) as SensorManager))
+    }
+
+    /** Lux from the default light sensor while listened to; an error at once without one, or when refused. */
+    private class LightStream(private val sm: SensorManager) : EventChannel.StreamHandler {
+        private var listener: SensorEventListener? = null
+
+        override fun onListen(arguments: Any?, events: EventChannel.EventSink) {
+            val sensor = sm.getDefaultSensor(Sensor.TYPE_LIGHT)
+                ?: return events.error("no_sensor", "no light sensor", null)
+            listener = object : SensorEventListener {
+                override fun onSensorChanged(e: SensorEvent) = events.success(e.values[0].toDouble())
+                override fun onAccuracyChanged(s: Sensor, accuracy: Int) {}
+            }
+            // The Redmi Pad SE lists one (derived from the front camera) but refuses apps:
+            // only the system's auto-brightness may read it.
+            if (!sm.registerListener(listener, sensor, SensorManager.SENSOR_DELAY_NORMAL)) {
+                listener = null
+                events.error("refused", "light sensor refused", null)
+            }
+        }
+
+        override fun onCancel(arguments: Any?) {
+            listener?.let { sm.unregisterListener(it) }
+            listener = null
+        }
     }
 
     private fun apply() {