macOS: support drag-handle config (#13709)

Closes https://github.com/ghostty-org/ghostty/discussions/12332

Also a tiny rephrasing for the documentation.

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -274,6 +274,16 @@ extension Ghostty {
             return v
         }
 
+        var dragHandle: DragHandle {
+            let defaultValue = DragHandle.auto
+            guard let config = self.config else { return defaultValue }
+            var v: UnsafePointer<Int8>?
+            let key = "drag-handle"
+            guard ghostty_config_get(config, &v, key, UInt(key.lengthOfBytes(using: .utf8))) else { return defaultValue }
+            guard let ptr = v else { return defaultValue }
+            return DragHandle(rawValue: String(cString: ptr)) ?? defaultValue
+        }
+
         /// Returns the fullscreen mode if fullscreen is enabled, or nil if disabled.
         /// This parses the `fullscreen` enum config which supports both
         /// native and non-native fullscreen modes.
@@ -933,4 +943,8 @@ extension Ghostty.Config {
         static let `default` = MacOSTitlebarStyle.transparent
         case native, transparent, tabs, hidden
     }
+
+    enum DragHandle: String {
+        case always, auto, never
+    }
 }

macos/Sources/Ghostty/Surface View/SurfaceGrabHandle.swift

@@ -10,11 +10,20 @@ extension Ghostty {
         private static let hoverHeightFactor: CGFloat = 0.2
 
         @ObservedObject var surfaceView: SurfaceView
+        let dragHandle: Ghostty.Config.DragHandle
 
         @State private var isHovering: Bool = false
         @State private var isDragging: Bool = false
 
         private var handleVisible: Bool {
+            switch dragHandle {
+            case .always:
+                return true
+            case .never:
+                return false
+            case .auto:
+                break
+            }
             // Handle should always be visible in non-fullscreen
             guard let window = surfaceView.window else { return true }
             guard window.styleMask.contains(.fullScreen) else { return true }
@@ -25,6 +34,14 @@ extension Ghostty {
         }
 
         private var ellipsisVisible: Bool {
+            switch dragHandle {
+            case .always:
+                return true
+            case .never:
+                return false
+            case .auto:
+                break
+            }
             // If the cursor isn't visible, never show the handle
             guard surfaceView.cursorVisible else { return false }
             // If we're hovering or actively dragging, always visible

macos/Sources/Ghostty/Surface View/SurfaceView.swift

@@ -205,7 +205,10 @@ extension Ghostty {
                 // top Z-index os it isn't faded by the unfocused overlay.
                 //
                 // This is disabled except on macOS because it uses AppKit drag/drop APIs.
-                SurfaceGrabHandle(surfaceView: surfaceView)
+                SurfaceGrabHandle(
+                    surfaceView: surfaceView,
+                    dragHandle: ghostty.config.dragHandle,
+                )
                 #endif
             }
         }

src/config/Config.zig

@@ -2356,8 +2356,13 @@ keybind: Keybinds = .{},
 ///
 ///  - `auto` *(default)*
 ///
-///    Automatically show and hide the drag handle. The handle is only
-///    shown when there are two or more splits present.
+///    Automatically show and hide the drag handle.
+///
+///    On Linux, the handle is only shown when there are two or
+///    more splits present.
+///
+///    On macOS, the handle is only hidden when there's one split
+///    in **fullscreen** mode, otherwise it's shown when hovered.
 ///
 ///  - `never`
 ///
@@ -2365,8 +2370,6 @@ keybind: Keybinds = .{},
 ///    mouse controls.
 ///
 /// Available since: 1.4.0.
-///
-/// Currently only supported on Linux (GTK).
 @"drag-handle": DragHandle = .auto,
 
 /// This controls when resize overlays are shown. Resize overlays are a