macos: enforce keyboard layout actor isolation

Text Input Sources APIs are not thread-safe, but shortcut translation could
be called outside a declared main-actor context.

Mark keyboard layout and shortcut conversion as main-actor isolated, update
their tests, and dispatch key-sequence UI notifications to the main queue
before translating their shortcuts.

macos/Sources/Ghostty/Ghostty.App.swift

@@ -1985,19 +1985,21 @@ extension Ghostty {
             case GHOSTTY_TARGET_SURFACE:
                 guard let surface = target.target.surface else { return }
                 guard let surfaceView = self.surfaceView(from: surface) else { return }
-                if v.active {
-                    NotificationCenter.default.post(
-                        name: Notification.didContinueKeySequence,
-                        object: surfaceView,
-                        userInfo: [
-                            Notification.KeySequenceKey: keyboardShortcut(for: v.trigger) as Any
-                        ]
-                    )
-                } else {
-                    NotificationCenter.default.post(
-                        name: Notification.didEndKeySequence,
-                        object: surfaceView
-                    )
+                DispatchQueue.main.async {
+                    if v.active {
+                        NotificationCenter.default.post(
+                            name: Notification.didContinueKeySequence,
+                            object: surfaceView,
+                            userInfo: [
+                                Notification.KeySequenceKey: keyboardShortcut(for: v.trigger) as Any
+                            ]
+                        )
+                    } else {
+                        NotificationCenter.default.post(
+                            name: Notification.didEndKeySequence,
+                            object: surfaceView
+                        )
+                    }
                 }
 
             default:

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -111,7 +111,7 @@ extension Ghostty {
         /// configuration would be "quit" action.
         ///
         /// Returns nil if there is no key equivalent for the given action.
-        func keyboardShortcut(for action: String) -> KeyboardShortcut? {
+        @MainActor func keyboardShortcut(for action: String) -> KeyboardShortcut? {
             guard let trigger = keybindTrigger(for: action) else { return nil }
             return Ghostty.keyboardShortcut(for: trigger)
         }

macos/Sources/Ghostty/Ghostty.Input.swift

@@ -16,7 +16,7 @@ extension Ghostty {
     /// (F1, F2, ...) with a KeyboardShortcut. This doesn't represent a practical issue because input
     /// handling for Ghostty is handled at a lower level (usually). This function should generally only
     /// be used for things like NSMenu that only support keyboard shortcuts anyways.
-    static func keyboardShortcut(for trigger: ghostty_input_trigger_s) -> KeyboardShortcut? {
+    @MainActor static func keyboardShortcut(for trigger: ghostty_input_trigger_s) -> KeyboardShortcut? {
         let modifierFlags = Self.eventModifierFlags(mods: trigger.mods)
         let key: KeyEquivalent
         switch trigger.tag {

macos/Sources/Helpers/KeyboardLayout.swift

@@ -16,7 +16,7 @@ class KeyboardLayout {
     /// Translate a physical keycode for use as a menu key equivalent.
     ///
     /// Must be called on the main thread because Text Input Sources APIs are not thread-safe.
-    static func character(
+    @MainActor static func character(
         for keyCode: UInt16,
         modifiers: NSEvent.ModifierFlags
     ) -> Character? {

macos/Tests/Ghostty/ConfigTests.swift

@@ -223,8 +223,8 @@ struct ConfigTests {
 
     // MARK: - Keybind
 
-    @Test
-    func uppercasedLetterShouldBeNormalized() async throws {
+    @MainActor @Test
+    func uppercasedLetterShouldBeNormalized() throws {
         let config = try TemporaryConfig("""
         keybind=cmd+L=goto_split:left
         """)
@@ -238,8 +238,8 @@ struct ConfigTests {
         #expect(shortcut2 == .init("ä", modifiers: [.command]))
     }
 
-    @Test
-    func emptyConfigShouldBeHaveDefaultShortcut() async throws {
+    @MainActor @Test
+    func emptyConfigShouldBeHaveDefaultShortcut() throws {
         let config = try TemporaryConfig("")
         let newWindow = try #require(config.keyboardShortcut(for: "new_window"))
         #expect(newWindow == .init("n", modifiers: [.command]))

macos/Tests/Ghostty/MenuShortcutManagerTests.swift

@@ -26,14 +26,14 @@ struct MenuShortcutManagerTests {
         #expect(item.keyEquivalentModifierMask == .command)
     }
 
-    @Test func physicalBackquoteUsesCurrentKeyboardLayout() async throws {
+    @MainActor @Test func physicalBackquoteUsesCurrentKeyboardLayout() throws {
         let config = try TemporaryConfig("keybind=super+backquote=toggle_quick_terminal")
         let expected = try #require(KeyboardLayout.character(for: 0x32, modifiers: .command))
         let item = NSMenuItem(title: "Quick Terminal", action: nil, keyEquivalent: "")
-        let manager = await Ghostty.MenuShortcutManager()
+        let manager = Ghostty.MenuShortcutManager()
 
-        await manager.reset()
-        await manager.syncMenuShortcut(config, action: "toggle_quick_terminal", menuItem: item)
+        manager.reset()
+        manager.syncMenuShortcut(config, action: "toggle_quick_terminal", menuItem: item)
 
         #expect(item.keyEquivalent == String(expected))
         #expect(item.keyEquivalentModifierMask == .command)