Distinguish unavailable radio signaling from an occupied call slot

tools/chatgui-android/router-tests/src/test/kotlin/com/utun/chat/data/RadioCallLifecycleTest.kt

@@ -10,6 +10,7 @@ import android.os.Looper
 import android.widget.Toast
 import androidx.core.app.NotificationCompat
 import com.utun.chat.ChatApplication
+import com.utun.chat.R
 import java.nio.ByteBuffer
 import java.nio.ByteOrder
 import java.util.concurrent.atomic.AtomicReference
@@ -333,4 +334,13 @@ class RadioCallLifecycleTest {
         assertTrue(RadioCallController.busy())
         emit(pending.id, 1, incoming = false); assertEquals(pending.id, state?.id)
     }
+
+    @Test fun stoppedCoreReportsUnavailableAndAnOngoingPhoneCallReportsBusy() {
+        RadioCallController.setVisible(true); NativeLib.ready = false
+        RadioCallController.start("7", 99)
+        assertEquals("en:${R.string.radio_call_unavailable}", Toast.shown.last()); assertTrue(calls.isEmpty())
+        NativeLib.ready = true; CallController.state.value = CallController.State(ongoing = true)
+        RadioCallController.start("7", 99)
+        assertEquals("en:${R.string.radio_call_busy}", Toast.shown.last()); assertTrue(calls.isEmpty())
+    }
 }