macos: use preference key to detect self dragging

macos/Sources/Features/Splits/TerminalSplitTreeView.swift

@@ -92,6 +92,7 @@ fileprivate struct TerminalSplitLeaf: View {
     let action: (TerminalSplitOperation) -> Void
     
     @State private var dropState: DropState = .idle
+    @State private var isSelfDragging: Bool = false
     
     var body: some View {
         GeometryReader { geometry in
@@ -105,11 +106,15 @@ fileprivate struct TerminalSplitLeaf: View {
                 action: action
             ))
             .overlay {
-                if case .dropping(let zone) = dropState {
+                if !isSelfDragging, case .dropping(let zone) = dropState {
                     zone.overlay(in: geometry)
                         .allowsHitTesting(false)
                 }
             }
+            .onPreferenceChange(Ghostty.DraggingSurfaceKey.self) { value in
+                Ghostty.logger.warning("BABY WE DRAGGING \(String(describing: value))")
+                isSelfDragging = value == surfaceView.id
+            }
             .accessibilityElement(children: .contain)
             .accessibilityLabel("Terminal pane")
         }

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

@@ -1,6 +1,16 @@
 import SwiftUI
 
 extension Ghostty {
+    /// A preference key that propagates the ID of the SurfaceView currently being dragged,
+    /// or nil if no surface is being dragged.
+    struct DraggingSurfaceKey: PreferenceKey {
+        static var defaultValue: SurfaceView.ID? = nil
+        
+        static func reduce(value: inout SurfaceView.ID?, nextValue: () -> SurfaceView.ID?) {
+            value = nextValue() ?? value
+        }
+    }
+    
     /// A grab handle overlay at the top of the surface for dragging the window.
     /// Only appears when hovering in the top region of the surface.
     struct SurfaceGrabHandle: View {
@@ -38,6 +48,7 @@ extension Ghostty {
             .draggable(surfaceView) {
                 SurfaceDragPreview(surfaceView: surfaceView, scale: previewScale)
             }
+            .preference(key: DraggingSurfaceKey.self, value: isDragging ? surfaceView.id : nil)
         }
     }