search: Remove 'x' from start node label

src/Search/Search.hs

@@ -66,11 +66,11 @@ findOpenDecision = listToMaybe . mapMaybe isHalf . M.elems . decisions
 
 driver :: FilePath -> IO ()
 driver prog = do
-  state <- newIORef (State M.empty (Just ("", "xstart")) M.empty [])
+  state <- newIORef (State M.empty (Just ("", "start")) M.empty [])
   oneProgRun prog state Nothing
 
   forever $ do
-    modifyIORef state $ \s -> s { curTrace = [], currentVertex = Just ("", "xstart") }
+    modifyIORef state $ \s -> s { curTrace = [], currentVertex = Just ("", "start") }
     findOpenDecision <$> readIORef state >>= \case
       Nothing    -> do
         s <- readIORef state