This improves handling of pasted content in the textarea. It's no longer possible to partially delete a placeholder (e.g. by ^W or ^D), nor is it possible to place the cursor inside a placeholder. Also, we now render placeholders in a different color to make them more clearly differentiated. https://github.com/user-attachments/assets/2051b3c3-963d-4781-a610-3afee522ae29