Preserve device timestamp offsets across output reopen and counter wrap

tools/chatgui-android/app/src/main/java/com/utun/chat/data/CallOutputRecovery.kt

@@ -32,5 +32,13 @@ internal class CallOutputPosition {
     }
 
     fun played(raw: Int, written: Long): Long? = head.update(raw, written - base)?.let { base + it }
-    fun timestamp(local: Long): Long = if (local < 0) -1 else base + local
+    fun timestamp(local: Long, written: Long): Long {
+        if (local < 0) return -1
+        var extended = local
+        if (local <= 0xffffffffL) {
+            extended = ((written - base) and -0x100000000L) or local
+            if (extended > written - base) extended -= 0x100000000L
+        }
+        return if (extended < 0) -1 else base + extended
+    }
 }