fix: call nativeSignalConnect from 8MB Java Thread, not Dispatchers.IO

android/app/src/main/java/com/wzp/ui/call/CallViewModel.kt

@@ -172,22 +172,26 @@ class CallViewModel : ViewModel(), WzpCallback {
         val seed = _seedHex.value
         val resolvedRelay = resolveToIp(relay) ?: relay
 
-        // nativeSignalConnect blocks up to 10s (waits for QUIC connect + register).
-        // Internal thread does the actual work; we just wait for the result.
-        viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
+        // nativeSignalConnect has JNI overhead — must be on a thread with enough stack.
+        // Dispatchers.IO threads overflow. Use explicit Java Thread.
+        Thread(null, {
             try {
                 val mgr = com.wzp.engine.SignalManager()
                 val ok = mgr.connect(resolvedRelay, seed)
-                if (ok) {
-                    signalManager = mgr
-                    startSignalPolling()
-                } else {
-                    _errorMessage.value = "Failed to register on relay"
+                viewModelScope.launch {
+                    if (ok) {
+                        signalManager = mgr
+                        startSignalPolling()
+                    } else {
+                        _errorMessage.value = "Failed to register on relay"
+                    }
                 }
             } catch (e: Exception) {
-                _errorMessage.value = "Register error: ${e.message}"
+                viewModelScope.launch {
+                    _errorMessage.value = "Register error: ${e.message}"
+                }
             }
-        }
+        }, "wzp-signal-init", 8 * 1024 * 1024).start()
     }
 
     /** Poll signal manager state every 500ms */