voice: fix waveform display + text buffer, 75% width, play/pause state

- bridge: txt buffer 256→2048, limit 250→2000 (voice d-field can be ~900 bytes)
- VoiceBubble: Column layout — play+waveform on top, duration|timestamp on bottom
- Play/pause toggle with ⏸/▶ icons
- Voice messages use 75% screen width max (300dp for others)

tools/chatgui-android/app/src/main/java/com/utun/chat/ui/components/MessageBubble.kt

@@ -37,6 +37,7 @@ fun MessageBubble(message: Message, onPlayVoice: (String) -> Unit = {}) {
     val textColor = if (message.isOutgoing) Color.White else Color.Black
     val alignment = if (message.isOutgoing) Arrangement.End else Arrangement.Start
     val minBubbleWidth = (LocalConfiguration.current.screenWidthDp / 3).dp
+    val voiceMaxWidth = (LocalConfiguration.current.screenWidthDp * 0.75f).dp
 
     val isVoice = message.contentType == "audio/opus"
     val isMedia = message.contentType.isNotEmpty() && !isVoice && message.contentType != "text/plain"
@@ -47,7 +48,7 @@ fun MessageBubble(message: Message, onPlayVoice: (String) -> Unit = {}) {
     ) {
         Column(
             modifier = Modifier
-                    .widthIn(min = minBubbleWidth, max = 300.dp)
+                    .widthIn(min = minBubbleWidth, max = if (isVoice) voiceMaxWidth else 300.dp)
                 .clip(RoundedCornerShape(12.dp))
                 .background(bgColor)
                 .padding(12.dp)
@@ -65,40 +66,51 @@ fun MessageBubble(message: Message, onPlayVoice: (String) -> Unit = {}) {
                 }
             }
 
-            Spacer(Modifier.height(2.dp))
-            Text(
-                formatTime(message.ts),
-                fontSize = 11.sp,
-                color = textColor.copy(alpha = 0.5f),
-                modifier = Modifier.align(Alignment.End)
-            )
+            if (!isVoice) {
+                Spacer(Modifier.height(2.dp))
+                Text(
+                    formatTime(message.ts),
+                    fontSize = 11.sp,
+                    color = textColor.copy(alpha = 0.5f),
+                    modifier = Modifier.align(Alignment.End)
+                )
+            }
         }
     }
 }
 
 @Composable
 private fun VoiceBubble(message: Message, textColor: Color, onPlay: (String) -> Unit) {
-    val durationSec = message.voiceDurationMs / 1000f
     val wf = message.waveform
     val wfCount = wf.size
+    val durMs = message.voiceDurationMs
+    val durSec = durMs / 1000f
+    var playing by remember { mutableStateOf(false) }
+    var elapsedMs by remember { mutableStateOf(0) }
 
-    Row(verticalAlignment = Alignment.CenterVertically) {
-        /* Play button */
-        Box(
-            modifier = Modifier.size(32.dp).background(Color(0xFF3390EC), CircleShape)
-                .clickable { if (message.filePath.isNotEmpty()) onPlay(message.filePath) },
-            contentAlignment = Alignment.Center
-        ) {
-            Text("\u25B6", fontSize = 14.sp, color = Color.White)
-        }
-        Spacer(Modifier.width(8.dp))
+    Column {
+        Row(verticalAlignment = Alignment.CenterVertically) {
+            /* Play/Pause button */
+            Box(
+                modifier = Modifier.size(32.dp).background(Color(0xFF3390EC), CircleShape)
+                    .clickable {
+                        if (!playing && message.filePath.isNotEmpty()) {
+                            playing = true; elapsedMs = 0; onPlay(message.filePath)
+                        } else {
+                            playing = false
+                        }
+                    },
+                contentAlignment = Alignment.Center
+            ) {
+                Text(if (playing) "\u23F8" else "\u25B6", fontSize = 14.sp, color = Color.White)
+            }
+            Spacer(Modifier.width(8.dp))
 
-        /* Waveform */
-        if (wfCount >= 2) {
-            Box(modifier = Modifier.weight(1f).height(32.dp)) {
-                Canvas(modifier = Modifier.fillMaxSize()) {
+            /* Waveform */
+            if (wfCount >= 2) {
+                Canvas(modifier = Modifier.weight(1f).height(28.dp)) {
                     val barW = size.width / wfCount
-                    val ph = size.height.toFloat()
+                    val ph = size.height
                     for (i in 0 until wfCount) {
                         val v = wf[i]
                         val db = if (v > 0.00001f) 20f * kotlin.math.log10(v.toDouble()).toFloat() else -100f
@@ -107,23 +119,35 @@ private fun VoiceBubble(message: Message, textColor: Color, onPlay: (String) ->
                         val x = i.toFloat() * barW
                         val y = ph - barH
                         drawRect(
-                            color = Color(0xFF3390EC).copy(alpha = 0.5f),
+                            color = Color(0xFF3390EC).copy(alpha = 0.35f),
                             topLeft = Offset(x, y),
-                            size = Size(barW * 0.8f, barH)
+                            size = Size(barW * 0.75f, barH)
                         )
                     }
                 }
             }
-            Spacer(Modifier.width(4.dp))
         }
 
-        /* Duration */
-        Text(
-            formatDurationMs(message.voiceDurationMs),
-            fontSize = 13.sp,
-            color = textColor.copy(alpha = 0.7f),
-            modifier = Modifier.padding(start = 4.dp)
-        )
+        Spacer(Modifier.height(4.dp))
+
+        /* Duration + timestamp */
+        Row(
+            modifier = Modifier.fillMaxWidth(),
+            horizontalArrangement = Arrangement.SpaceBetween,
+            verticalAlignment = Alignment.Bottom
+        ) {
+            Text(
+                formatDurationMs(durMs),
+                fontSize = 12.sp,
+                color = textColor.copy(alpha = 0.55f)
+            )
+            Text(
+                formatTime(message.ts),
+                fontSize = 11.sp,
+                color = textColor.copy(alpha = 0.4f),
+                modifier = Modifier.align(Alignment.CenterVertically).padding(start = 8.dp)
+            )
+        }
     }
 }