Revert "fix(tui): 初始化时自动聚焦 textarea + 颜色/按键改动"

恢复到 b1ad99c 版本的 TuiApp.tsx。
Enter/换行/颜色改动全部回退，保持原始 TUI 行为。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/tui/src/TuiApp.tsx

@@ -254,11 +254,6 @@ function AirCodingView(props: {
   let pasteTick: ReturnType<typeof setTimeout> | undefined
   let exitConfirmUntil = 0
 
-  onMount(() => {
-    // Give the textarea time to mount before focusing
-    setTimeout(() => focusPrompt(), 50)
-  })
-
   props.bindState({
     setProjection,
     setView: setActiveView,