Keep latest messages above composer (desktop)

fix for desktop: keep latest messages above composer

**Steps to reproduce**
1. Go to any chat
2. Wait for agent to respond with messages
3. Look at the input the tip section on top is covering latest messages

**Expected behavior**
I expected the messages to not go under the tip section the message container should end either on top of the tip section instead of on top of the composer or the tip section should have a cross icon in the right to close it.

**Version and platform**
Find your version at the bottom of the Settings sidebar. Write "unknown" if you can't determine it.
- Buzz version: v0.5.8
- OS: Windows 11

**Logs / additional context**

Start in the desktop chat view, focusing on the message container, composer, and tip section described in the reproduction steps. Reproduce the overlap on Windows 11 with Buzz v0.5.8, then verify that the latest messages remain visible above the tip section and composer.

Written by the indexing model from the issue text.