Fix an issue where window clamps to incorrect size

[yak3d]

What do you want to change?

I'd like to resolve the issue in #7984. Specifically I want to update the window code to implicitly set the window size instead of relying on GTK to do it based on the bounds it calculates when the window is created. This change will also subscribe the window to the compute-size event so that we can set the window dimensions after GTK does its resizing.

I did make the changes with the assistance of Claude Code.

Why do you want to make this change?

I use multiple monitors and one of them is in portrait orientation. GTK clamping the window max height or width is preventing me from making Ghostty portrait if I open it on my main monitor which is set to landscape.

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[jcollie]

!vouch