fix: 修复 Config 面板第二次进入时左右键无反应的问题

将左右键枚举值切换从依赖 DOM 焦点的 onKeyDown 改为 useKeybindings 系统，
确保按键在任何焦点状态下都能正确响应。同时修复 isSearchMode 初始值和布局问题。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/keybindings/schema.ts

@@ -168,6 +168,8 @@ export const KEYBINDING_ACTIONS = [
   'settings:search',
   'settings:retry',
   'settings:close',
+  'select:previousValue',
+  'select:nextValue',
   // Voice actions
   'voice:pushToTalk',
 ] as const