gtk: Resizes due to tiling cause text to stretch/flicker

[cuddleplush]

Issue

In a tiling environment, such as a tiling window manager or wayland compositor, windows often get resized quickly. Most windows/terminals handle this well, but when a ghostty window gets resized in this way, the currently visible text will appear to "stretch" or flicker for a split second, which can be pretty jarring.

Possibly related: #2446

Repro

Default config, tile a ghostty window in a twm.

Showcase

Look at the prompt of the terminal window that's currently being resized due to tiling.
https://github.com/user-attachments/assets/fc6a985c-9231-4781-81e6-58815c9dff3f

[mitchellh]

I’ll consider this a dupe of 2446 as linked