cmux Ghostty

GhosttyKit builds

When rebuilding GhosttyKit.xcframework, always use Release optimizations:

cd ghostty && zig build -Demit-xcframework=true -Dxcframework-target=universal -Doptimize=ReleaseFast

Submodule workflow

Ghostty changes must be committed in the ghostty submodule and pushed to the manaflow-ai/ghostty fork. Keep docs/ghostty-fork.md up to date with any fork changes and conflict notes.