[Bug] Agent harnesses screen is not scrollable

**Describe the bug**
I just set up the app and got to the Agent harnesses screen. Installing Claude Code failed with an error, which made the content so tall that it did no longer fit into the window height. And I realized that I cannot scroll. I use a MacBook Pro (16 inch) with a second monitor attached. On the MacBook, I cannot reach the lower part of the screen, including the "Finish" button and am stuck.

**To Reproduce:**
See above.

**Expected behavior:**
Vertical scrolling should be possible.

**Supporting Material**

**Environment (please complete the following information):**
- OS: MacOS
- Version: Buzz Desktop v0.4.6

**Additional context**
Add any other context that you feel is relevant about the problem here.

Start at the Agent harnesses screen and reproduce the setup flow on macOS with a failed Claude Code installation so the content exceeds the window height. Inspect that screen's layout and scrolling behavior; done means the lower content and the Finish button are reachable by vertical scrolling.

Written by the indexing model from the issue text.