Vouch request: Mask consumed modifiers for character bindings

[qappell]

What do you want to change?

I would like to update how Ghostty handles consumed modifiers during keyboard shortcut matching to fix layout-dependent character bindings. For example, ctrl + + currently fails on Linux US layouts because Ghostty reads it strictly as ctrl + shift + + (due to the shift key being held). This addresses the fix recommended in this discussion comment: #7243 (comment).

With this change, Ghostty evaluates Unicode bindings using the produced character plus only the unconsumed modifiers. It will recognize ctrl + + whether a user types it with a dedicated physical key or uses Shift/AltGr to produce the symbol. It doesn't break default letter-based keybinds.

I have the PR ready locally. It updates Binding.zig to mask consumed modifiers before matching, using the data GTK provides on Linux. I also updated the Swift NSEvent extension to compute consumed modifiers on macOS by directly comparing characters with and without Shift/Option via AppKit APIs. Since I am on NixOS and don't have a macOS machine, someone will need to verify the macOS side still works as expected after I open the PR.

Why do you want to make this change?

I was looking into why ctrl + + wasn't working to zoom in on my Linux machine even though it is a default bind (I was used to it working fine on Kitty). That led me to discover the discussion my PR will address: #7243 (comment).

While adding ctrl+shift+equal or ctrl+shift+plus to the defaults would be an easy hack, implementing proper modifier consumption permanently fixes character bindings for all international layouts and puts Ghostty's Linux input handling on par with macOS. It makes bindings feel more humanly predictable.

My motivation also comes from how awesome Ghostty is! Its rendering is top-notch, and I found out about it after watching The Primeagen's recent video on Zig.

I acknowledge that:

• I have read the Contributing Guide and understand the contribution process.
• I have read and agree to follow the AI Usage Policy.
• I wrote this vouch request myself, in my own voice, without AI generating it.

[qappell]

I got a Mac a few weeks ago and have learned enough about Swift and AppKit to make much more valuable changes. I've toiled for many hours and you can preview my changes at https://github.com/qappell/ghostty/tree/modifier-consumption before vouching me.

[tristan957]

!vouch qappell