feat: implement game board rendering and spaceship player control

- Create 10x20 game board grid with retro styling
- Render spaceship emoji at player position (bottom center)
- Implement cursor movement with hjkl (left/right only)
- Add moveToStart (0) and moveToEnd ($) anchor motions
- Re-render board when cursor position changes
- Board displays dark grid with highlighted player row

example/src/App.tsx

@@ -3,19 +3,24 @@ import { useGame } from "@vimazing/typing-chud";
 import "@vimazing/typing-chud/game.css";
 import type { GameManager } from "@vimazing/typing-chud";
 import { useKeyBindings } from "./useKeyBindings";
+import { useMounted } from "./useMounted";
 
 function App() {
   const gameManager = useGame({}, useKeyBindings);
-  const { containerRef, gameStatus, scoreManager, renderBoard } = gameManager;
+  const { containerRef, gameStatus, scoreManager, renderBoard, cursor } = gameManager;
   const gameManagerRef = useRef<GameManager>(gameManager);
+  const [mounted] = useMounted();
 
   useEffect(() => {
     gameManagerRef.current = gameManager;
   }, [gameManager]);
 
+  // Re-render board when cursor position changes
   useEffect(() => {
-    renderBoard();
-  }, [renderBoard]);
+    if (mounted) {
+      renderBoard();
+    }
+  }, [cursor.position(), renderBoard, mounted]);
 
   const formatTime = (ms: number) => {
     const seconds = Math.floor(ms / 1000);