mac: title bar fix 1px none covered video at top

there is 1px border at the top of the window that is not covered by our
title bar and the video below is visible. this broke in some newer macOS
version even so the calculation of size and position of the title bar is
still correct. add 1px the the height of the title bar to cover up the
unwanted border.

video/out/mac/title_bar.swift

@@ -49,7 +49,7 @@ class TitleBar: NSVisualEffectView {
 
     init(frame: NSRect, window: NSWindow, common com: Common) {
         let f = NSMakeRect(0, frame.size.height - TitleBar.height,
-                           frame.size.width, TitleBar.height)
+                           frame.size.width, TitleBar.height + 1)
         common = com
         super.init(frame: f)
         buttons.forEach { $0.isHidden = true }