simplify Live Call audio: remove MODE_IN_COMMUNICATION

MODE_IN_COMMUNICATION activates the telephony DSP pipeline which
degrades audio quality and requires setCommunicationDevice hacks for
speaker routing. The Gemini reference implementation doesn't use it.

Echo protection now relies on:
1. VOICE_COMMUNICATION AudioSource (built-in AEC/AGC/NS)
2. AcousticEchoCanceler on AudioRecord session (hardware AEC)
3. Hard ducking (zero mic chunks during model speech)

AudioTrack stays USAGE_ASSISTANT for full-quality speaker output.
This matches the WebRTC.ventures Gemini prototype architecture.

app/src/main/java/dev/kaizen/app/live/AudioPipeline.kt

@@ -5,7 +5,6 @@ import android.content.Context
 import android.content.pm.PackageManager
 import android.media.AudioAttributes
 import android.media.AudioFormat
-import android.media.AudioManager
 import android.media.AudioRecord
 import android.media.AudioTrack
 import android.media.MediaRecorder
@@ -52,8 +51,6 @@ class AudioPipeline(private val context: Context) {
     var onChunk: ((base64Pcm: String) -> Unit)? = null
     var onAmplitude: ((Float) -> Unit)? = null
 
-    private val audioManager = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
-    private var previousAudioMode = AudioManager.MODE_NORMAL
     private var recorder: AudioRecord? = null
     private var track: AudioTrack? = null
     private var aec: AcousticEchoCanceler? = null
@@ -62,35 +59,6 @@ class AudioPipeline(private val context: Context) {
     @Volatile private var ducking = false
     @Volatile private var capturing = false
 
-    // ─── Audio Mode ───────────────────────────────────────────────────────
-
-    fun enterCallMode() {
-        previousAudioMode = audioManager.mode
-        audioManager.mode = AudioManager.MODE_IN_COMMUNICATION
-
-        if (android.os.Build.VERSION.SDK_INT >= 31) {
-            val speaker = audioManager.availableCommunicationDevices
-                .firstOrNull { it.type == android.media.AudioDeviceInfo.TYPE_BUILTIN_SPEAKER }
-            if (speaker != null) {
-                audioManager.setCommunicationDevice(speaker)
-                Log.i(TAG, "Communication device → speaker")
-            }
-        } else {
-            @Suppress("DEPRECATION")
-            audioManager.isSpeakerphoneOn = true
-        }
-    }
-
-    fun exitCallMode() {
-        if (android.os.Build.VERSION.SDK_INT >= 31) {
-            audioManager.clearCommunicationDevice()
-        } else {
-            @Suppress("DEPRECATION")
-            audioManager.isSpeakerphoneOn = false
-        }
-        audioManager.mode = previousAudioMode
-    }
-
     // ─── Capture ──────────────────────────────────────────────────────────
 
     fun startCapture(scope: CoroutineScope): Boolean {
@@ -243,7 +211,6 @@ class AudioPipeline(private val context: Context) {
     fun release() {
         stopCapture()
         stopPlayback()
-        exitCallMode()
     }
 
     // ─── Helpers ──────────────────────────────────────────────────────────

app/src/main/java/dev/kaizen/app/live/LiveCallService.kt

@@ -168,7 +168,6 @@ class LiveCallService : Service() {
                 connectTimeoutJob?.cancel()
                 _status.value = CallStatus.LISTENING
 
-                pipeline.enterCallMode()
                 if (!pipeline.initPlayback()) {
                     Log.e(TAG, "Playback init failed")
                 }