screen rendering glitches

### Issue

this happens occasionally:

<img width="778" height="102" alt="Image" src="https://github.com/user-attachments/assets/f0ba123c-17d2-4512-80e0-731465d18fdd" />

### Version and model info

Aider v0.88.2.101.dev+less
Main model: gemini/gemini-2.5-pro with diff edit format
Weak model: gemini/gemini-2.5-flash-lite
Git repo: .git with 115 files
Repo-map: using 4096 tokens, auto refresh
