android: round send button with \u27A4 icon (matching desktop chatgui)

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

@@ -5,8 +5,9 @@ import android.content.pm.PackageManager
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.background
-import androidx.compose.foundation.interaction.MutableInteractionSource
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.*
 import androidx.compose.runtime.*
@@ -223,8 +224,19 @@ fun InputBar(
 
             if (!isRecording) {
                 Spacer(Modifier.width(4.dp))
-                Button(onClick = onSend, enabled = enabled && text.isNotBlank()) {
-                    Text("Send")
+                val sendColor = MaterialTheme.colorScheme.primary
+                val sendEnabled = enabled && text.isNotBlank()
+                Box(
+                    modifier = Modifier
+                        .size(44.dp)
+                        .background(
+                            if (sendEnabled) sendColor else sendColor.copy(alpha = 0.35f),
+                            CircleShape
+                        )
+                        .clickable { if (sendEnabled) onSend() },
+                    contentAlignment = Alignment.Center
+                ) {
+                    Text("\u27A4", fontSize = 22.sp, color = Color.White)
                 }
             }
         }