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).