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

docs/rewrite/DEVIANT_FIXES.md

@@ -89,7 +89,7 @@ Only entries with an observable behavioural difference are listed.
 
 | Area | Zig/Ghostty behaviour | Rust behaviour | Where | Commit |
 |------|-----------------------|----------------|-------|--------|
-| Swift macOS app | Ships `macos/` | Not ported; the Rust side provides the `libghostty` C API, Metal/CoreText code, XCFramework script. Only compile-checked (`just check-macos`), never run (no macOS here). | `ARCHITECTURE.md` (Out of scope), `notes/macos-M1*.md`, `final-Z4.md` | bab49ee, 75bf604, 231ee35 |
+| Swift macOS app | Ships `macos/` (Swift/SwiftUI/xib, Xcode, Sparkle, App Intents) | Ported to Rust/AppKit in `crates/ghostty-macos` (programmatic AppKit instead of xib/SwiftUI; menu tables generated from `MainMenu.xib`; bundle assembled by `scripts/macos-bundle.sh`). Only compile-checked (`just check-macos`), never run (no macOS here). Deviations (menu quirks kept, no nib loading, config background fallback, byte-length URL in `open_config`, non-compatible `CodableBridge` archives, ...) are listed in `notes/macos-app-MA1.md`; App Intents is unportable from Rust (`notes/macos-app-design.md`). The Rust side also still provides the `libghostty` C API for the unchanged Swift app. | `notes/macos-app-design.md`, `notes/macos-app-MA1.md`, `ARCHITECTURE.md`, `notes/macos-M1*.md` | (uncommitted) |
 | Windows (and wasm natively) | Native targets | Windows is compile-checked only (`just check-windows`), never run. wasm is built and its Node smoke/ABI tests run (`just check-wasm`, `scripts/wasm-check.sh`), but not in a real browser. | `notes/windows-WIN.md`, `notes/wasm-W1.md` | 76771be, d89691b |
 | Crash reporting | Sentry with Breakpad on macOS, `SIGSEGV` handlers, local DB/cache, sessions, init thread | In-process reporter: `.ghosttycrash` envelopes in `$XDG_STATE_HOME/ghostty/crash`, panic hook and signal handler, minidumps on macOS/Windows. No Sentry DB/cache dir, no sessions, no init thread; reports are written on any panic; the crash dir is resolved at init; the signal path writes no attachment. | `notes/crash-CR.md`, `ARCHITECTURE.md` (Scope changes) | b3145ad, 72bfac1 |
 | Surface copy-on-select on release | `setSelection` returns early when the new selection equals the old one | Left-release copies directly via `copy_on_select`, because the early return would never copy | `notes/ghostty-core.md` | ad76ae2 |