fix: address remaining Copilot review comments

- AndroidCodec2Encoder: VAD returns null instead of ByteArray(0) to prevent
  empty packet transmission; fix stale KDoc ref (Codec2Jni -> Codec2JNI)
- AndroidAudioPlayer: fix mojibake encoding in comments
- VoiceBurstViewModel: ENCODING_FAILED -> RECORDING_FAILED in recorder error
  path; fix 'broadcasted' log to 'sent to \'; fix mojibake in KDoc
- VoiceBurstButton: remove reference to non-existent isVisible property
- FeatureVoiceBurstAndroidModule: remove dead ref to FeatureAchievementsAndroidModule
- Codec2Jni: replace duplicate JNI class with typealias to Codec2JNI

feature/voiceburst/src/androidMain/kotlin/org/meshtastic/codec2/Codec2Jni.kt

@@ -17,38 +17,8 @@
 package org.meshtastic.codec2
 
 /**
- * JNI wrapper for the Codec2 library.
- * This class is the interface between Kotlin/JVM and the C codec logic.
+ * Backwards-compatible alias to the canonical Codec2 JNI wrapper used by
+ * the voiceburst feature. The actual implementation lives in
+ * [com.geeksville.mesh.voiceburst.Codec2JNI].
  */
-class Codec2Jni {
-
-    /**
-     * Encodes 16-bit mono PCM audio (8kHz) into Codec2 compressed frames.
-     * @param pcm Input audio data (ShortArray)
-     * @return Compressed byte array or null on error
-     */
-    external fun encode(pcm: ShortArray): ByteArray?
-
-    /**
-     * Decodes Codec2 compressed frames back into 16-bit mono PCM audio (8kHz).
-     * @param compressed Compressed audio data (ByteArray)
-     * @return Decoded ShortArray or null on error
-     */
-    external fun decode(compressed: ByteArray): ShortArray?
-
-    /**
-     * Gets the current Codec2 mode (e.g., 3200, 2400, etc.).
-     */
-    external fun getMode(): Int
-
-    companion object {
-        init {
-            try {
-                System.loadLibrary("codec2_jni")
-            } catch (e: UnsatisfiedLinkError) {
-                // Logger not available in this core-module, using println
-                println("Critical: Could not load codec2_jni library")
-            }
-        }
-    }
-}
+typealias Codec2Jni = com.geeksville.mesh.voiceburst.Codec2JNI

feature/voiceburst/src/androidMain/kotlin/org/meshtastic/feature/voiceburst/audio/AndroidAudioPlayer.kt

@@ -34,12 +34,12 @@ private const val TAG = "AndroidAudioPlayer"
 /**
  * Android implementation of [AudioPlayer].
  *
- * Fixes compared to previous versions:
- *  - BUG: MODE_STATIC with bufferSize < minBufferSize → STATE_NO_STATIC_DATA (state=2) → silence.
+ * Key implementation notes:
+ *  - BUG: MODE_STATIC with bufferSize < minBufferSize -> STATE_NO_STATIC_DATA (state=2) -> silence.
  *    FIX: bufferSize = maxOf(minBufferSize, pcmBytes) ALWAYS, even in static mode.
  *  - Using MODE_STREAM: simpler and avoids the STATE_NO_STATIC_DATA issue.
  *    For 1 second at 8kHz (16000 bytes) MODE_STREAM is more than adequate.
- *  - USAGE_MEDIA → main speaker (not earpiece).
+ *  - USAGE_MEDIA -> main speaker (not earpiece).
  *  - [playingFilePath] StateFlow to sync play/stop icons in the UI.
  */
 class AndroidAudioPlayer(
@@ -63,7 +63,7 @@ class AndroidAudioPlayer(
         }
 
         if (pcmData.isEmpty()) {
-            Logger.w(tag = TAG) { "PCM data is empty — skipping playback" }
+            Logger.w(tag = TAG) { "PCM data is empty -- skipping playback" }
             onComplete()
             return
         }
@@ -80,7 +80,7 @@ class AndroidAudioPlayer(
         }
 
         // CRITICAL: bufferSize must always be >= minBufferSize.
-        // With MODE_STATIC, if bufferSize < minBufferSize → state=STATE_NO_STATIC_DATA=2 → silence.
+        // With MODE_STATIC, if bufferSize < minBufferSize -> state=STATE_NO_STATIC_DATA=2 -> silence.
         // MODE_STREAM is used for simplicity and robustness.
         val pcmBytes   = pcmData.size * Short.SIZE_BYTES
         val bufferSize = maxOf(minBufferSize, pcmBytes)

feature/voiceburst/src/androidMain/kotlin/org/meshtastic/feature/voiceburst/codec/AndroidCodec2Encoder.kt

@@ -29,18 +29,18 @@ private const val TAG = "AndroidCodec2Encoder"
 /**
  * Android implementation of [Codec2Encoder].
  *
- * When [Codec2Jni.isAvailable] = true, uses libcodec2 via JNI (real voice audio).
+ * When [Codec2JNI.isAvailable] is true, uses libcodec2 via JNI (real voice audio).
  * Otherwise falls back to STUB mode (440Hz sine wave) for development/CI/builds without .so.
  *
  * Codec2 700B parameters:
  *   - Sample rate input:  8000 Hz
  *   - Frame:              40ms = 320 samples
  *   - Bytes per frame:    4
- *   - 1 second:           25 frames × 4 bytes = 100 bytes
+ *   - 1 second:           25 frames x 4 bytes = 100 bytes
  *
  * Preprocessing applied before encoding (JNI mode only):
  *   1. Amplitude normalization (brings to 70% of Short.MAX_VALUE)
- *   2. Simple VAD: if RMS < threshold, returns silence without encoding
+ *   2. Simple VAD: if RMS < threshold, returns null without encoding
  *
  * JNI Lifecycle:
  *   The Codec2 handle is created in the constructor and destroyed in [close()].
@@ -63,14 +63,14 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
                         " bytesPerFrame=${Codec2JNI.getBytesPerFrame(Codec2JNI.MODE_700C)}"
                 }
             } else {
-                Logger.e(tag = TAG) { "Codec2JNI.create() returned 0 — falling back to stub mode" }
+                Logger.e(tag = TAG) { "Codec2JNI.create() returned 0 -- falling back to stub mode" }
                 codec2Handle = 0L
                 isStub = true
             }
         } else {
             codec2Handle = 0L
             isStub = true
-            Logger.w(tag = TAG) { "Codec2 JNI not available — stub mode (440Hz sine wave)" }
+            Logger.w(tag = TAG) { "Codec2 JNI not available -- stub mode (440Hz sine wave)" }
         }
     }
 
@@ -81,17 +81,17 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         }
     }
 
-    // ─── encode ───────────────────────────────────────────────────────────────
+    // --- encode -------------------------------------------------------------
 
     /**
      * Encodes 16-bit mono 8000Hz PCM into Codec2 700B bytes.
      *
-     * Accepts an array of any length — it is split into frames
+     * Accepts an array of any length -- it is split into frames
      * of [SAMPLES_PER_FRAME] samples. The last incomplete frame is
      * padded with zeros (zero-padding).
      *
      * @param pcmData  PCM samples from the microphone (8000 Hz, mono, signed 16-bit)
-     * @return         ByteArray with Codec2 bytes, null if input is empty
+     * @return         ByteArray with Codec2 bytes, null if input is empty or silence detected
      */
     override fun encode(pcmData: ShortArray): ByteArray? {
         if (pcmData.isEmpty()) return null
@@ -110,11 +110,11 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         // Preprocessing: normalization
         val normalized = normalize(pcmData)
 
-        // VAD: do not send silence
+        // VAD: do not send silence -- return null so the ViewModel skips transmission
         val rms = computeRms(normalized)
         if (rms < SILENCE_RMS_THRESHOLD) {
-            Logger.d(tag = TAG) { "VAD: silence detected (RMS=$rms) — skipping encode" }
-            return ByteArray(0)
+            Logger.d(tag = TAG) { "VAD: silence detected (RMS=$rms) -- skipping encode" }
+            return null
         }
 
         // Calculate needed frames (round up)
@@ -132,7 +132,6 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
             } else {
                 ShortArray(samplesPerFrame).also {
                     normalized.copyInto(it, 0, inStart, inEnd)
-                    // remaining already 0 by default
                 }
             }
 
@@ -147,13 +146,13 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         }
 
         Logger.d(tag = TAG) {
-            "Encode JNI: ${pcmData.size} samples → ${output.size} bytes " +
-                "($frameCount frames × $bytesPerFrame bytes)"
+            "Encode JNI: ${pcmData.size} samples -> ${output.size} bytes " +
+                "($frameCount frames x $bytesPerFrame bytes)"
         }
         return output
     }
 
-    // ─── decode ───────────────────────────────────────────────────────────────
+    // --- decode -------------------------------------------------------------
 
     /**
      * Decodes Codec2 700B bytes into 16-bit mono 8000Hz PCM samples.
@@ -178,7 +177,7 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         if (codec2Data.size % bytesPerFrame != 0) {
             Logger.w(tag = TAG) {
                 "Decode: input size (${codec2Data.size}) not a multiple of " +
-                    "bytesPerFrame ($bytesPerFrame) — truncating to complete frame"
+                    "bytesPerFrame ($bytesPerFrame) -- truncating to complete frame"
             }
         }
 
@@ -203,16 +202,16 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         }
 
         Logger.d(tag = TAG) {
-            "Decode JNI: ${codec2Data.size} bytes → ${output.size} samples " +
-                "($frameCount frames × $samplesPerFrame samples)"
+            "Decode JNI: ${codec2Data.size} bytes -> ${output.size} samples " +
+                "($frameCount frames x $samplesPerFrame samples)"
         }
         return output
     }
 
-    // ─── Preprocessing helpers ────────────────────────────────────────────────
+    // --- Preprocessing helpers ----------------------------------------------
 
     /**
-     * Normalizes the signal amplitude to [TARGET_AMPLITUDE] × Short.MAX_VALUE.
+     * Normalizes the signal amplitude to [TARGET_AMPLITUDE] x Short.MAX_VALUE.
      * Prevents clipping and improves Codec2 quality on low-volume voices.
      */
     private fun normalize(pcm: ShortArray): ShortArray {
@@ -220,7 +219,6 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         if (maxAmp < 1f) return pcm  // absolute silence
 
         val gain = (TARGET_AMPLITUDE * Short.MAX_VALUE) / maxAmp
-        // Limit maximum gain to 10x to avoid excessive noise amplification
         val clampedGain = minOf(gain, MAX_GAIN)
 
         return ShortArray(pcm.size) { i ->
@@ -238,12 +236,12 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         return sqrt(sumSquares / pcm.size)
     }
 
-    // ─── Stub (fallback when JNI is not available) ─────────────────────────
+    // --- Stub (fallback when JNI is not available) --------------------------
 
     private fun encodeStub(pcmData: ShortArray): ByteArray {
         val frameCount = (pcmData.size + SAMPLES_PER_FRAME - 1) / SAMPLES_PER_FRAME
         Logger.w(tag = TAG) {
-            "Codec2 STUB encode: ${pcmData.size} samples → ${frameCount * BYTES_PER_FRAME} bytes (zeros)"
+            "Codec2 STUB encode: ${pcmData.size} samples -> ${frameCount * BYTES_PER_FRAME} bytes (zeros)"
         }
         return ByteArray(frameCount * BYTES_PER_FRAME) { 0x00 }
     }
@@ -253,10 +251,10 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         val totalSamples = frameCount * SAMPLES_PER_FRAME
 
         Logger.w(tag = TAG) {
-            "Codec2 STUB decode: ${codec2Data.size} bytes → $totalSamples samples (440Hz sine wave)"
+            "Codec2 STUB decode: ${codec2Data.size} bytes -> $totalSamples samples (440Hz sine wave)"
         }
 
-        // Generate 440Hz sine wave (A4) — audible and recognizable
+        // Generate 440Hz sine wave (A4) -- audible and recognizable
         val sampleRate = 8000.0
         val frequency  = 440.0
         val amplitude  = Short.MAX_VALUE * 0.3  // 30% volume
@@ -277,12 +275,12 @@ class AndroidCodec2Encoder : Codec2Encoder, AutoCloseable {
         /** Target amplitude for normalization (70% of Short.MAX_VALUE). */
         private const val TARGET_AMPLITUDE = 0.70f
 
-        /** Maximum gain applied by normalization (10×). */
+        /** Maximum gain applied by normalization (10x). */
         private const val MAX_GAIN = 10.0f
 
         /**
          * RMS threshold below which the frame is considered silence (simple VAD).
-         * 200.0 on the 0-32767 scale is approximately -44 dBFS — normal voice is 2000-8000.
+         * 200.0 on the 0-32767 scale is approximately -44 dBFS -- normal voice is 2000-8000.
          */
         private const val SILENCE_RMS_THRESHOLD = 200.0
     }

feature/voiceburst/src/androidMain/kotlin/org/meshtastic/feature/voiceburst/di/FeatureVoiceBurstAndroidModule.kt

@@ -43,7 +43,7 @@ import org.meshtastic.feature.voiceburst.repository.VoiceBurstRepository
 /**
  * Koin module for the Voice Burst feature module.
  *
- * Follows the same pattern as [FeatureAchievementsAndroidModule]:
+ * Follows the standard Android feature-module pattern:
  *   - Context and Android-only APIs remain in androidMain
  *   - commonMain has no direct Android dependencies
  */

feature/voiceburst/src/commonMain/kotlin/org/meshtastic/feature/voiceburst/ui/VoiceBurstButton.kt

@@ -54,8 +54,9 @@ import org.jetbrains.compose.resources.stringResource
 /**
  * PTT (Push-To-Talk) button for Voice Burst.
  *
- * Visible only if [VoiceBurstViewModel.isVisible] == true (feature flag enabled).
- * Disabled during encoding/sending/rate limit.
+ * Render this composable only when Voice Burst is available; callers should not render
+ * it for [VoiceBurstState.Unsupported].
+ * Disabled during non-interactive processing states such as encoding and sending.
  *
  * Visual states:
  *   Idle       -> Mic icon, normal color

feature/voiceburst/src/commonMain/kotlin/org/meshtastic/feature/voiceburst/ui/VoiceBurstViewModel.kt

@@ -44,8 +44,8 @@ private const val TAG = "VoiceBurstViewModel"
  * ViewModel handling the lifecycle and orchestration of Voice Burst messaging.
  *
  * Full pipeline:
- *   MIC → [AudioRecorder] → PCM → [Codec2Encoder.encode] → bytes → [VoiceBurstRepository.sendBurst]
- *   RADIO → [VoiceBurstRepository.incomingBursts] → bytes → [Codec2Encoder.decode] → PCM → [AudioPlayer]
+ *   MIC -> [AudioRecorder] -> PCM -> [Codec2Encoder.encode] -> bytes -> [VoiceBurstRepository.sendBurst]
+ *   RADIO -> [VoiceBurstRepository.incomingBursts] -> bytes -> [Codec2Encoder.decode] -> PCM -> [AudioPlayer]
  *
  * Rate limiting is enforced: minimum [RATE_LIMIT_MS] between consecutive bursts.
  *
@@ -103,7 +103,7 @@ class VoiceBurstViewModel(
             .launchIn(viewModelScope)
     }
 
-    // ─── Receiver-side logic ────────────────────────────────────────────────
+    // --- Receiver-side logic ------------------------------------------------
 
     private fun onBurstReceived(payload: VoiceBurstPayload) {
         Logger.i(tag = TAG) {
@@ -114,7 +114,7 @@ class VoiceBurstViewModel(
 
         val pcmData = encoder.decode(payload.audioData)
         if (pcmData == null || pcmData.isEmpty()) {
-            Logger.e(tag = TAG) { "Decoding failed — no PCM samples to play" }
+            Logger.e(tag = TAG) { "Decoding failed -- no PCM samples to play" }
             _state.update { VoiceBurstState.Idle }
             return
         }
@@ -128,7 +128,7 @@ class VoiceBurstViewModel(
         }
     }
 
-    // ─── Sender-side (PTT) recording ──────────────────────────────────────
+    // --- Sender-side (PTT) recording ----------------------------------------
 
     /**
      * Initiates microphone recording if the state machine is [Idle].
@@ -183,7 +183,7 @@ class VoiceBurstViewModel(
                 uiTimerJob?.cancel()
                 uiTimerJob = null
                 Logger.e(tag = TAG) { "Hardware recording error: ${error.message}" }
-                _state.update { VoiceBurstState.Error(VoiceBurstError.ENCODING_FAILED) }
+                _state.update { VoiceBurstState.Error(VoiceBurstError.RECORDING_FAILED) }
             },
             maxDurationMs = MAX_DURATION_MS,
         )
@@ -201,7 +201,7 @@ class VoiceBurstViewModel(
         audioRecorder.stopRecording()
     }
 
-    // ─── Encoding and Dispatch ──────────────────────────────────────────────
+    // --- Encoding and Dispatch ----------------------------------------------
 
     internal fun onRecordingComplete(pcmData: ShortArray, durationMs: Int) {
         _state.update { VoiceBurstState.Encoding }
@@ -215,9 +215,9 @@ class VoiceBurstViewModel(
             }
 
             if (encoder.isStub) {
-                Logger.w(tag = TAG) { "Running with Codec2 stub — transmission will not be intelligible" }
+                Logger.w(tag = TAG) { "Running with Codec2 stub -- transmission will not be intelligible" }
             } else {
-                Logger.i(tag = TAG) { "Enc JNI Success: ${pcmData.size} samples → ${audioBytes.size} bytes" }
+                Logger.i(tag = TAG) { "Enc JNI Success: ${pcmData.size} samples -> ${audioBytes.size} bytes" }
             }
 
             val payload = VoiceBurstPayload(