feat: 新增 /pokemon-battle 独立战斗命令，从 BuddyPanel 移除 Battle tab

- 新增 /pokemon-battle 命令，独立全屏战斗面板
- BattlePanel 在主 app Ink 上下文中使用 useInput，通过 inputRef 转发事件
- BuddyPanel 恢复为 Buddy/Pokédex/Egg 三 tab
- BattleFlow 移除内部 useInput，改为暴露 handleInput 方法

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/commands/pokemon-battle/index.ts

@@ -0,0 +1,15 @@
+import type { Command } from '../../commands.js'
+import { isBuddyLive } from '../../buddy/useBuddyNotification.js'
+
+const pokemonBattle = {
+  type: 'local-jsx',
+  name: 'pokemon-battle',
+  description: 'Start a Pokémon battle',
+  immediate: true,
+  get isHidden() {
+    return !isBuddyLive()
+  },
+  load: () => import('./pokemon-battle.js'),
+} satisfies Command
+
+export default pokemonBattle