chore: add ghostty-apprt crate for core/runtime contract types

crates/ghostty-apprt/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "ghostty-apprt"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+ghostty-vt.workspace = true
+ghostty-input.workspace = true
+ghostty-config.workspace = true
+ghostty-datastruct.workspace = true
+
+[lints]
+workspace = true

crates/ghostty-apprt/src/lib.rs

@@ -0,0 +1 @@
+//! ghostty-apprt: the contract between the core and app runtimes (ZIG/src/apprt/{action,structs,surface,ipc}.zig).

docs/rewrite/ARCHITECTURE.md

@@ -22,6 +22,7 @@ WASM, Windows and the embedded C API (`libghostty`) are out of scope.
 | `ghostty-termio` | termio/*, pty.zig, Command.zig, shell-integration resources | config, terminal, os |
 | `ghostty-cli` | cli/* actions (+list-themes, +show-config, +list-keybinds, ...) | config, input, os, font |
 | `ghostty-core` | App.zig, Surface.zig, surface_mouse.zig, apprt/action.zig, apprt/structs.zig, apprt/surface.zig, global.zig | everything below |
+| `ghostty-apprt` | apprt/action.zig, structs.zig, surface.zig, ipc.zig (core↔runtime contract types) | vt, input, config, datastruct |
 | `ghostty-apprt-gtk` | apprt/gtk/* | core, config, input |
 | root `ghostty-rs` (bin `ghostty`) | main_ghostty.zig, build_config.zig | core, config, apprt-gtk |