feat: position hardware cursor

- add cursor marker extraction for rendered lines

- move the terminal cursor after full and differential renders

- update input to use the real cursor instead of a block glyph

src/Example/Program.cs

@@ -42,8 +42,7 @@ page.Add(new Box(eventsText, textMeasurer) { Title = "事件" });
 
 runtime.Add(page);
 runtime.SetFocus(input);
-
-terminalOutput.HideCursor();
+terminalOutput.ShowCursor();
 
 try
 {