macOS: update window appearance for About and ConfigurationErrors (#12601)

<img width="1224" height="696" alt="Xnip2026-05-06_19-13-31"
src="https://github.com/user-attachments/assets/ab090dc0-7c06-4a01-8e7c-5d48ca6ccca3"
/>

macos/Sources/Features/About/AboutController.swift

@@ -13,6 +13,7 @@ class AboutController: NSWindowController, NSWindowDelegate {
         window.center()
         window.isMovableByWindowBackground = true
         window.contentView = NSHostingView(rootView: AboutView().environmentObject(viewModel))
+        window.titlebarAppearsTransparent = true
     }
 
     // MARK: - Functions

macos/Sources/Features/Settings/ConfigurationErrorsController.swift

@@ -29,5 +29,6 @@ class ConfigurationErrorsController: NSWindowController, NSWindowDelegate, Confi
         window.center()
         window.level = .popUpMenu
         window.contentView = NSHostingView(rootView: ConfigurationErrorsView(model: self))
+        window.titlebarAppearsTransparent = true
     }
 }

macos/Sources/Features/Settings/ConfigurationErrorsView.swift

@@ -46,8 +46,11 @@ struct ConfigurationErrorsView<ViewModel: ConfigurationErrorsViewModel>: View {
             HStack {
                 Spacer()
                 Button("Ignore") { model.errors = [] }
+                    .keyboardShortcut(.cancelAction)
                 Button("Reload Configuration") { reloadConfig() }
+                    .keyboardShortcut(.defaultAction)
             }
+            .controlSize(.large)
             .padding([.bottom, .trailing])
         }
         .frame(minWidth: 480, maxWidth: 960, minHeight: 270)