feat: add differential renderer

- track previous rendered lines and terminal size

- redraw only changed rows after the initial full render

- expose redraw counters in the example

src/Example/Program.cs

@@ -11,10 +11,10 @@ using var terminalInput = new ConsoleTerminalInput();
 var terminalOutput = new ConsoleTerminalOutput();
 var parser = new DefaultInputParser();
 var textMeasurer = new TerminalTextMeasurer();
-var renderer = new FullScreenRenderer(terminalOutput, textMeasurer);
+var renderer = new DifferentialRenderer(terminalOutput, textMeasurer);
 using var runtime = new TuiRuntime(terminalInput, parser, renderer);
 
-var component = new EchoComponent(runtime, textMeasurer);
+var component = new EchoComponent(runtime, textMeasurer, renderer);
 runtime.Add(component);
 runtime.SetFocus(component);
 
@@ -36,7 +36,7 @@ finally
 /// <summary>
 /// 用于手动验证 Runtime 的示例组件
 /// </summary>
-file sealed class EchoComponent(ITuiRuntime runtime, ITextMeasurer textMeasurer) : IInputComponent
+file sealed class EchoComponent(ITuiRuntime runtime, ITextMeasurer textMeasurer, DifferentialRenderer renderer) : IInputComponent
 {
     private readonly ManualResetEventSlim _done = new();
     private readonly List<string> _events = [];
@@ -49,6 +49,8 @@ file sealed class EchoComponent(ITuiRuntime runtime, ITextMeasurer textMeasurer)
             "TinyTUI Runtime 示例",
             "====================",
             $"当前渲染宽度: {width}",
+            $"全量重绘次数: {renderer.FullRedrawCount}",
+            $"差分重绘次数: {renderer.DifferentialRedrawCount}",
             string.Empty,
             "测试方式:",
             "- 输入普通字符 验证 Text 事件会进入焦点组件",