I've implemented a GTK toggle (gtk-horizontal-tab-scroll) for the
2-finger tab swiping introduced in #10575.
This resolves the issue presented in #11566. Simply put, this allows
users to decide whether or not they want to use horizontal tab scrolling
or just have the events passed through. Passing through the horizontal
scroll events allows programs like Neovim to use them for horizontal
scrolling.
This PR was largely generated by Claude Code and fully reviewed/refined
by me.
e5b65a2ce3