Task list scrollbar is hidden when content overflows

Description

When the expanded task list exceeds its maximum height, it can be scrolled with the mouse wheel, but no scrollbar or other scroll indicator is visible.

This makes it difficult to discover that additional tasks exist below the visible area.

Expected: show a subtle scrollbar when the task list overflows.
Actual: the list scrolls, but the scrollbar remains hidden.

Plugins

None

OpenCode version

OpenCode Desktop v1.18.9

Steps to reproduce

1. Start a session in the desktop app.
2. Ask the model to create enough tasks to exceed the task list's maximum height (for example, 10 tasks).
3. Expand the task list above the prompt input.
4. Scroll inside the task list.
5. Observe that the list scrolls, but no scrollbar is visible.

Screenshot and/or share link

https://github.com/user-attachments/assets/43ef89a9-03d8-4722-8b8f-b58a4755ccd8

Attached video demonstrates the task list scrolling without a visible scrollbar.

Operating System

Windows 11

Terminal

None