[Bug/Enhancement] No highlight when selecting snippet placeholder

[imhuay]

Description
When using the Dracula theme in VS Code, snippet placeholders (e.g. $1) can be filled normally. However, when selecting the inserted text with Shift + ←/→, the selected part has no visual distinction from the surrounding text. It looks like the selection is not applied.

https://github.com/user-attachments/assets/23ff244a-0c91-47c0-bcc0-804c4ab54f1c

https://github.com/user-attachments/assets/d7ded54e-fcff-4d85-bdeb-2958c51fd28f

Steps to Reproduce

1. Enable the Dracula theme in VS Code.
2. Insert a user snippet containing a $1 placeholder.
3. Type into the $1 position.
4. Use Shift + ←/→ to select the text.
5. Observe the selection effect.

Expected Behavior
The selected text should be visually highlighted and clearly distinguished from the surrounding text.

Actual Behavior
The selected text has no visible highlight, making it indistinguishable from unselected text.