Fix a performance rendering size miscalculation in the pager example

examples/pager/main.go

@@ -101,10 +101,15 @@ func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			// quickly, though asynchronously, which is why we wait for them
 			// here.
 			m.viewport = viewport.Model{Width: msg.Width, Height: msg.Height - verticalMargins}
-			m.viewport.YPosition = headerHeight
 			m.viewport.HighPerformanceRendering = useHighPerformanceRenderer
 			m.viewport.SetContent(m.content)
 			m.ready = true
+
+			// This is only necessary for high performance rendering, which in
+			// most cases you won't need.
+			//
+			// Render the viewport one line below the header.
+			m.viewport.YPosition = headerHeight + 1
 		} else {
 			m.viewport.Width = msg.Width
 			m.viewport.Height = msg.Height - verticalMargins