Swiftlint for swift parts of Ghostty

[cristeahub]

I suggest adding swiftlint https://github.com/realm/SwiftLint (or any other linter) to the swift/macos/ios parts of ghostty.

Linters (and formatters) has become a normal part of development and helps enforce style and conventions. Having this for ghostty would be a big help when working on the swift part of the project.

Swiftlint specifically also allows for formatting by running swiftlint lint --format. It also has good guides for setup in all parts of mac development (i.e. on CI, during build phase, in the terminal etc).

What needs to be done before starting this

This list might not be exhaustive

• Land what linting tool to use
• Land on a convention/set of rules to apply

Caveats

When creating and merging these types of lint PR-s you usually get a lot of merge conflicts. So starting this after tools and conventions has landed helps with this. In addition this should be done when the Ghostty team is ready to get it merged, so a PR won't be stuck in review for too long, which will make it become "stale" (i.e. merge conflicts).

In addition other PR-s that are not merged yet will quickly need a rebase due to styling changes after the lint PR is merged.

[Aaron-212]

I suggest using Swift Format https://github.com/swiftlang/swift-format. It is embedded in to Xcode 16, thus no additional packages is required to install. You can run it from command line by calling swift format or pressing Control + Shift + I in Xcode.