macos: add AppleScript new window command

Add a `new window` command to the scripting dictionary and wire it to
`NSApplication` so AppleScript can create Ghostty windows.

The command returns a scripting `window` object for the created window,
with a fallback to a direct wrapper when AppKit window ordering has not
yet refreshed in the current run loop.

macos/Ghostty.sdef

@@ -13,6 +13,9 @@
       <responds-to command="perform action">
         <cocoa method="handlePerformActionScriptCommand:"/>
       </responds-to>
+      <responds-to command="new window">
+        <cocoa method="handleNewWindowScriptCommand:"/>
+      </responds-to>
       <responds-to command="quit">
         <cocoa method="handleQuitScriptCommand:"/>
       </responds-to>
@@ -71,6 +74,10 @@
       <result type="boolean" description="True when the action was performed."/>
     </command>
 
+    <command name="new window" code="GhstNWin" description="Create a new Ghostty window.">
+      <result type="window" description="The newly created window."/>
+    </command>
+
     <enumeration name="split direction" code="GSpD" description="Direction for a new split.">
       <enumerator name="right" code="GSrt" description="Split to the right."/>
       <enumerator name="left" code="GSlf" description="Split to the left."/>

macos/Sources/Features/AppleScript/AppDelegate+AppleScript.swift

@@ -125,6 +125,32 @@ extension NSApplication {
 
         return NSNumber(value: terminal.perform(action: action))
     }
+
+    /// Handler for the `new window` AppleScript command.
+    ///
+    /// Required selector name from the command in `sdef`:
+    /// `handleNewWindowScriptCommand:`.
+    ///
+    /// Returns the newly created scripting window object.
+    @objc(handleNewWindowScriptCommand:)
+    func handleNewWindowScriptCommand(_ command: NSScriptCommand) -> Any? {
+        guard let appDelegate = delegate as? AppDelegate else {
+            command.scriptErrorNumber = errAEEventFailed
+            command.scriptErrorString = "Ghostty app delegate is unavailable."
+            return nil
+        }
+
+        let controller = TerminalController.newWindow(appDelegate.ghostty)
+        let createdWindowID = ScriptWindow.stableID(primaryController: controller)
+
+        if let scriptWindow = scriptWindows.first(where: { $0.stableID == createdWindowID }) {
+            return scriptWindow
+        }
+
+        // Fall back to wrapping the created controller if AppKit window ordering
+        // has not refreshed yet in the current run loop.
+        return ScriptWindow(primaryController: controller)
+    }
 }
 
 // MARK: - Private Helpers