When collapse, index arrow still points down

[nicfv]

Search terms

index, collapsible, arrow

Expected Behavior

When I collapse the index group, the arrow should point right.

Actual Behavior

The arrow points down.

Steps to reproduce the bug

1. Visit example website: https://typedoc.org/example/classes/CancellablePromise.html
2. Click on v Index
3. Expect > Index

Environment

• Typedoc version: 0.27.6
• TypeScript version: 5.7.3
• Node.js version: 20.17.0
• OS: Ubuntu 24.04