Flickering rocks in background of hidden game (logo easter egg)

### Short summary

Background rocks flicker in the hidden easter egg game accessed via the app logo, after jumping up a few platforms.

### Affected version or release

v1.1.10

### Installation context

AppImage installation on Linux amd64, Wayland session. Visual glitch scoped to the hidden game screen only.

### What happened?

After clicking the app logo to open the hidden game, landing on the first platform, scrolling down so the prompt input is out of view, and jumping across a few platforms, the rocks in the background start flickering.

### Steps to reproduce

1. Open the app
2. Click the app logo to open the hidden game
3. Land on the first platform
4. Scroll down so the prompt input field is out of view
5. Jump across a few platforms to gain some height
6. Rocks appear in the background
7. The rocks start flickering

### Expected behavior

Background rocks should render normally and not flicker.

### Additional context

_No response_

从隐藏游戏的 app-logo 入口点开始，在将 prompt 滚动到视野外并跳跃穿过平台后重现闪烁现象。跟踪 Linux Wayland 上背景岩石的渲染路径，然后验证岩石在相同序列中保持稳定，并且隐藏游戏仍能正常渲染。

由索引模型根据 Issue 内容生成。