feat(macos): foundation of the macOS app ported from Swift to Rust

Phase 9, MA1: crates/ghostty-macos (AppKit via objc2; empty stub on
non-Apple targets) ports the foundation of Ghostty 1.3.1's Swift macOS
app (ghostty/macos): main, AppDelegate (+Ghostty) with lifecycle, dock
menu, open-file, notifications, shortcut sync and quit/reopen paths;
MainMenu.xib as generated menu tables built into NSMenus; the
Ghostty.App/Config/Surface wrappers driving libghostty in-process via
ghostty-lib; the generic helpers; scripts/macos-bundle.sh to assemble
Ghostty.app (dry-run on Linux). Feature areas are stubbed for MA2-MA5.
Design and type mapping: docs/rewrite/notes/macos-app-design.md
(App Intents is a Swift-only framework and cannot be ported).

Compile-checked only (no macOS here): just check-macos passes for
aarch64/x86_64-apple-darwin with -D warnings; 125 platform-independent
tests run on Linux.

Test Plan:
- just check-macos
- cargo test -p ghostty-macos

crates/ghostty-macos/src/features/terminal/mod.rs

@@ -0,0 +1,178 @@
+//! `Sources/Features/Terminal`: terminal windows and their controllers.
+//!
+//! TODO(MA3): this file is the *foundation stub* written by MA1 so that
+//! `Ghostty.App`'s action glue and the app delegate compile. It declares the
+//! classes with the API surface they use, logs `TODO(MA3)` and returns
+//! conservative values. MA3 replaces every body with the real port of
+//! `BaseTerminalController.swift`, `TerminalController.swift`,
+//! `Window Styles/TerminalWindow.swift` etc., keeping these signatures.
+#![cfg(target_vendor = "apple")]
+// Stubs: bodies do not use `self` yet.
+#![allow(clippy::unused_self)]
+
+use std::{
+    cell::{Cell, RefCell},
+    rc::Rc,
+};
+
+use log::warn;
+use objc2::{DefinedClass, MainThreadOnly, define_class, rc::Retained};
+use objc2_app_kit::{NSResponder, NSWindow, NSWindowController};
+use objc2_foundation::NSObject;
+
+use crate::ghostty::{
+    app::App,
+    package::SplitFocusDirection,
+    surface_configuration::SurfaceConfiguration,
+    surface_view::SurfaceView,
+};
+
+/// Instance variables of [`BaseTerminalController`].
+#[derive(Default)]
+pub struct BaseTerminalControllerIvars {
+    /// `bell` (TODO(MA3): published, drives the title bell indicator).
+    pub bell: Cell<bool>,
+    /// `titleOverride`.
+    pub title_override: RefCell<Option<String>>,
+}
+
+define_class!(
+    /// `BaseTerminalController`: the base class of all terminal window controllers.
+    // SAFETY: NSWindowController has no subclassing requirements we violate;
+    // no Drop impl.
+    #[unsafe(super(NSWindowController, NSResponder, NSObject))]
+    #[thread_kind = MainThreadOnly]
+    #[name = "GhosttyBaseTerminalController"]
+    #[ivars = BaseTerminalControllerIvars]
+    pub struct BaseTerminalController;
+);
+
+impl BaseTerminalController {
+    /// `surfaceTree.isSplit`.
+    #[must_use]
+    pub fn surface_tree_is_split(&self) -> bool {
+        warn!("TODO(MA3): BaseTerminalController::surface_tree_is_split");
+        false
+    }
+
+    /// `surfaceTree.focusTarget(for:from:) != nil` for the node holding `view`
+    /// (App.gotoSplit's performability check).
+    #[must_use]
+    pub fn focus_target_exists(
+        &self,
+        _direction: SplitFocusDirection,
+        _view: &SurfaceView,
+    ) -> bool {
+        warn!("TODO(MA3): BaseTerminalController::focus_target_exists");
+        false
+    }
+
+    /// `surfaceTree` as a flat list of its surface views (iterating the tree).
+    #[must_use]
+    pub fn surface_tree(&self) -> Vec<Retained<SurfaceView>> {
+        warn!("TODO(MA3): BaseTerminalController::surface_tree");
+        Vec::new()
+    }
+
+    /// `focusedSurface`.
+    #[must_use]
+    pub fn focused_surface(&self) -> Option<Retained<SurfaceView>> {
+        warn!("TODO(MA3): BaseTerminalController::focused_surface");
+        None
+    }
+
+    /// `toggleBackgroundOpacity()`.
+    pub fn toggle_background_opacity(&self) {
+        warn!("TODO(MA3): BaseTerminalController::toggle_background_opacity");
+    }
+
+    /// `promptTabTitle()`.
+    pub fn prompt_tab_title(&self) {
+        warn!("TODO(MA3): BaseTerminalController::prompt_tab_title");
+    }
+
+    /// `titleOverride = ...`.
+    pub fn set_title_override(&self, title: Option<String>) {
+        *self.ivars().title_override.borrow_mut() = title;
+        warn!("TODO(MA3): BaseTerminalController::set_title_override (title not applied)");
+    }
+
+    /// `bell`.
+    #[must_use]
+    pub fn bell(&self) -> bool {
+        self.ivars().bell.get()
+    }
+
+    /// `relabelTabs()`.
+    pub fn relabel_tabs(&self) {
+        warn!("TODO(MA3): BaseTerminalController::relabel_tabs");
+    }
+}
+
+define_class!(
+    /// `TerminalController`: the controller of a regular terminal window.
+    // SAFETY: as above.
+    #[unsafe(super(BaseTerminalController, NSWindowController, NSResponder, NSObject))]
+    #[thread_kind = MainThreadOnly]
+    #[name = "GhosttyTerminalController"]
+    #[ivars = ()]
+    pub struct TerminalController;
+);
+
+impl TerminalController {
+    /// `TerminalController.all`: every terminal controller, in creation order.
+    #[must_use]
+    pub fn all() -> Vec<Retained<TerminalController>> {
+        Vec::new()
+    }
+
+    /// `TerminalController.newWindow(_:withBaseConfig:)`.
+    #[must_use]
+    pub fn new_window(
+        _ghostty: &Rc<App>,
+        _base_config: Option<&SurfaceConfiguration>,
+    ) -> Option<Retained<TerminalController>> {
+        warn!("TODO(MA3): TerminalController::new_window");
+        None
+    }
+
+    /// `TerminalController.newTab(_:from:withBaseConfig:)`.
+    #[must_use]
+    pub fn new_tab(
+        _ghostty: &Rc<App>,
+        _from: Option<&NSWindow>,
+        _base_config: Option<&SurfaceConfiguration>,
+    ) -> Option<Retained<TerminalController>> {
+        warn!("TODO(MA3): TerminalController::new_tab");
+        None
+    }
+
+    /// `TerminalController.preferredParent`.
+    #[must_use]
+    pub fn preferred_parent() -> Option<Retained<TerminalController>> {
+        None
+    }
+
+    /// `TerminalController.closeAllWindows()`.
+    pub fn close_all_windows() {
+        warn!("TODO(MA3): TerminalController::close_all_windows");
+    }
+}
+
+/// `TerminalWindow.defaultLevelKey`.
+pub const DEFAULT_LEVEL_KEY: &str = "TerminalDefaultLevel";
+
+define_class!(
+    /// `TerminalWindow`: the NSWindow subclass of terminal windows.
+    // SAFETY: as above.
+    #[unsafe(super(NSWindow, NSResponder, NSObject))]
+    #[thread_kind = MainThreadOnly]
+    #[name = "GhosttyTerminalWindow"]
+    #[ivars = ()]
+    pub struct TerminalWindow;
+);
+
+impl TerminalWindow {
+    /// `TerminalWindow.defaultLevelKey`.
+    pub const DEFAULT_LEVEL_KEY: &'static str = DEFAULT_LEVEL_KEY;
+}