Make DOM operations for highlights more efficient

A lot of time is spent clearing highlights even when no highlights are happening. The DOM is stupid and slow but one way or another it should be easy to avoid this.

<img width="531" height="180" alt="Image" src="https://github.com/user-attachments/assets/4b7e289d-8793-4cc2-bcc0-a4db5ddc0ddf" />