build: fix macOS 26 SDK compatibility for App Intents

Add compile-time SDK version checking to conditionally compile macOS 26
features, allowing the project to build on macOS 15.

- Add SUPPORTS_MACOS_26_FEATURES macro in bridging header
- Wrap App Intents supportedModes properties with conditional compilation
- Fix TransparentTitlebarTerminalWindow method calls

macos/Sources/App/macOS/ghostty-bridging-header.h

@@ -1,3 +1,12 @@
 // C imports here are exposed to Swift.
 
 #import "VibrantLayer.h"
+
+// SDK version check for macOS 26 features
+#import <AvailabilityMacros.h>
+
+// Check if SDK version is macOS 26 or higher
+// macOS 26.0 would be 260000 in the version macro
+#if __MAC_OS_X_VERSION_MAX_ALLOWED >= 260000
+    #define SUPPORTS_MACOS_26_FEATURES 1
+#endif

macos/Sources/Features/App Intents/CloseTerminalIntent.swift

@@ -12,8 +12,10 @@ struct CloseTerminalIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = .background
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult {

macos/Sources/Features/App Intents/CommandPaletteIntent.swift

@@ -19,8 +19,10 @@ struct CommandPaletteIntent: AppIntent {
     )
     var command: CommandEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = .background
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult & ReturnsValue<Bool> {

macos/Sources/Features/App Intents/GetTerminalDetailsIntent.swift

@@ -17,8 +17,10 @@ struct GetTerminalDetailsIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = .background
+    #endif
 
     static var parameterSummary: some ParameterSummary {
         Summary("Get \(\.$detail) from \(\.$terminal)")

macos/Sources/Features/App Intents/InputIntent.swift

@@ -24,8 +24,10 @@ struct InputTextIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = [.background, .foreground]
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult {
@@ -74,8 +76,10 @@ struct KeyEventIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = [.background, .foreground]
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult {
@@ -136,8 +140,10 @@ struct MouseButtonIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = [.background, .foreground]
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult {
@@ -197,8 +203,10 @@ struct MousePosIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = [.background, .foreground]
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult {
@@ -265,8 +273,10 @@ struct MouseScrollIntent: AppIntent {
     )
     var terminal: TerminalEntity
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = [.background, .foreground]
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult {

macos/Sources/Features/App Intents/KeybindIntent.swift

@@ -16,8 +16,10 @@ struct KeybindIntent: AppIntent {
     )
     var action: String
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = [.background, .foreground]
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult & ReturnsValue<Bool> {

macos/Sources/Features/App Intents/NewTerminalIntent.swift

@@ -43,8 +43,10 @@ struct NewTerminalIntent: AppIntent {
     )
     var parent: TerminalEntity?
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = .foreground(.immediate)
+    #endif
 
     @available(macOS, obsoleted: 26.0, message: "Replaced by supportedModes")
     static var openAppWhenRun = true

macos/Sources/Features/App Intents/QuickTerminalIntent.swift

@@ -5,8 +5,10 @@ struct QuickTerminalIntent: AppIntent {
     static var title: LocalizedStringResource = "Open the Quick Terminal"
     static var description = IntentDescription("Open the Quick Terminal. If it is already open, then do nothing.")
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     static var supportedModes: IntentModes = .background
+    #endif
 
     @MainActor
     func perform() async throws -> some IntentResult & ReturnsValue<[TerminalEntity]> {

macos/Sources/Features/Terminal/Window Styles/TransparentTitlebarTerminalWindow.swift

@@ -67,13 +67,14 @@ class TransparentTitlebarTerminalWindow: TerminalWindow {
         // references changed (e.g. tabGroup is new).
         setupKVO()
 
-        if #available(macOS 26.0, *) {
+        #if SUPPORTS_MACOS_26_FEATURES
-            syncAppearanceTahoe(surfaceConfig)
+        syncAppearanceTahoe(surfaceConfig)
-        } else {
+        #else
-            syncAppearanceVentura(surfaceConfig)
+        syncAppearanceVentura(surfaceConfig)
-        }
+        #endif
     }
 
+    #if SUPPORTS_MACOS_26_FEATURES
     @available(macOS 26.0, *)
     private func syncAppearanceTahoe(_ surfaceConfig: Ghostty.SurfaceView.DerivedConfig) {
         // When we have transparency, we need to set the titlebar background to match the
@@ -94,6 +95,7 @@ class TransparentTitlebarTerminalWindow: TerminalWindow {
         // that force a background color.
         titlebarBackgroundView?.isHidden = true
     }
+    #endif
 
     @available(macOS 13.0, *)
     private func syncAppearanceVentura(_ surfaceConfig: Ghostty.SurfaceView.DerivedConfig) {