Slow UI performance on linux

[smltr]

Describe the bug
The UI is very sluggish on linux. Things such as the automatic highlighting style change after hovering a message can take a half second.

Steps to reproduce

1. Open the app
2. Get an agent to start working on something
3. Scroll
4. Notice it takes significant time before scrolling happens
   Expected behavior
   What did you expect to happen?

Version and platform
Find your version at the bottom of the Settings sidebar. Write "unknown" if you can't determine it.

• Buzz version: v0.4.26
• OS: Linux Mint

Logs / additional context
Seems to be affected by whether or not an agent is running (worse when agent running)

[jordancannon88]

Reproduced on Fedora 42 (GNOME Wayland), v0.5.3 AppImage. Sluggish scrolling and delayed hover highlights.

Tested:

1. WEBKIT_DISABLE_DMABUF_RENDERER=1 and GDK_BACKEND=x11: marginal. Expected, since 0.5.3 already applies the dmabuf workaround when running as an AppImage (webkit_rendering.rs).
2. Disabling agent typing indicator broadcasts on the relay side: minimal improvement while agents work.
3. Rebuilding the same tag as an rpm in a Fedora 42 container, linked against the system WebKitGTK (Skia renderer): this fixed the issue for me. Scrolling is smooth. The WebKit bundled into the AppImage is the callout. A newer bundled WebKit, or official rpm or flatpak packages, should resolve this issue.

Only issue with the rpm build is the scrolling is slightly slower inside a thread view.