fix(map): add world plane collision and respawn

src/world/WorldPlane.tsx

@@ -0,0 +1,20 @@
+import { WORLD_BOUNDS_CONFIG } from "@/data/world/worldBoundsConfig";
+
+export function WorldPlane(): React.JSX.Element | null {
+  if (!WORLD_BOUNDS_CONFIG.enabled) {
+    return null;
+  }
+
+  const { center, planeColor, planeY, size } = WORLD_BOUNDS_CONFIG;
+
+  return (
+    <mesh
+      name="world-plane"
+      position={[center[0], planeY, center[2]]}
+      rotation={[-Math.PI / 2, 0, 0]}
+    >
+      <planeGeometry args={size} />
+      <meshBasicMaterial color={planeColor} />
+    </mesh>
+  );
+}