fix: mic mute crackling + add AEC/NoiseSuppressor + dedup room participants

Mic mute: the send loop now zeros the capture buffer when muted instead
of relying on write_audio() to skip writes. Previously stale ring data
and AGC amplification of near-silence caused crackling artifacts.

AEC: attach Android's hardware AcousticEchoCanceler to the AudioRecord
session. Also attach NoiseSuppressor when available. Both are released
on capture stop.

Room UI: deduplicate participants by fingerprint so ghost entries from
stale relay state don't show duplicate names.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/wzp/audio/AudioPipeline.kt

@@ -8,6 +8,8 @@ import android.media.AudioFormat
 import android.media.AudioRecord
 import android.media.AudioTrack
 import android.media.MediaRecorder
+import android.media.audiofx.AcousticEchoCanceler
+import android.media.audiofx.NoiseSuppressor
 import android.util.Log
 import androidx.core.content.ContextCompat
 import com.wzp.engine.WzpEngine
@@ -127,8 +129,34 @@ class AudioPipeline(private val context: Context) {
             return
         }
 
+        // Attach hardware AEC if available
+        var aec: AcousticEchoCanceler? = null
+        if (AcousticEchoCanceler.isAvailable()) {
+            try {
+                aec = AcousticEchoCanceler.create(recorder.audioSessionId)
+                aec?.enabled = true
+                Log.i(TAG, "AEC enabled (session=${recorder.audioSessionId})")
+            } catch (e: Exception) {
+                Log.w(TAG, "AEC init failed: ${e.message}")
+            }
+        } else {
+            Log.w(TAG, "AEC not available on this device")
+        }
+
+        // Attach hardware noise suppressor if available
+        var ns: NoiseSuppressor? = null
+        if (NoiseSuppressor.isAvailable()) {
+            try {
+                ns = NoiseSuppressor.create(recorder.audioSessionId)
+                ns?.enabled = true
+                Log.i(TAG, "NoiseSuppressor enabled")
+            } catch (e: Exception) {
+                Log.w(TAG, "NoiseSuppressor init failed: ${e.message}")
+            }
+        }
+
         recorder.startRecording()
-        Log.i(TAG, "capture started: ${SAMPLE_RATE}Hz mono, buf=$bufSize")
+        Log.i(TAG, "capture started: ${SAMPLE_RATE}Hz mono, buf=$bufSize, aec=${aec?.enabled}, ns=${ns?.enabled}")
 
         val pcm = ShortArray(FRAME_SAMPLES)
         try {
@@ -144,6 +172,8 @@ class AudioPipeline(private val context: Context) {
             }
         } finally {
             recorder.stop()
+            aec?.release()
+            ns?.release()
             recorder.release()
             Log.i(TAG, "capture stopped")
         }

crates/wzp-android/src/engine.rs

@@ -339,6 +339,12 @@ async fn run_call(
                 continue;
             }
 
+            // Mute: zero out the buffer so Opus encodes silence.
+            // We still read from the ring to prevent it from filling up.
+            if state.muted.load(Ordering::Relaxed) {
+                capture_buf.fill(0);
+            }
+
             // AGC: normalize capture volume before encoding
             capture_agc.process_frame(&mut capture_buf);