feat: Phase 2 — 战斗引擎 @pkmn 薄适配层

- 安装 @pkmn/protocol @pkmn/client @pkmn/view
- 新建 battle/types.ts: BattleState, BattlePokemon, BattleEvent, PlayerAction 等
- 新建 battle/adapter.ts: Creature→PokemonSet 转换, 野生对手生成
- 新建 battle/engine.ts: createBattle() + executeTurn() 薄封装 @pkmn/sim
- 新建 battle/handler.ts: @pkmn/protocol Handler→BattleEvent 转换
- 新建 battle/ai.ts: 随机合法招式 AI 决策
- 新建 battle/settlement.ts: 战后结算 XP/EV/升级/进化/招式学习
- 新建 battle/index.ts: 统一导出

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

packages/pokemon/src/index.ts

@@ -36,6 +36,12 @@ export { getNextEvolution, EVOLUTION_CHAINS } from './data/evolution'
 export { getDefaultMoveset, getDefaultAbility, getNewLearnableMoves } from './data/learnsets'
 export { FROM_DEX_STAT, TO_DEX_STAT } from './data/pkmn'
 
+// Battle
+export type { BattleState, BattlePokemon, BattleEvent, BattleResult, PlayerAction, MoveOption, StatusCondition } from './battle/types'
+export { createBattle, executeTurn, type BattleInit } from './battle/engine'
+export { settleBattle, applyMoveLearn, applyEvolution } from './battle/settlement'
+export { chooseAIMove } from './battle/ai'
+
 // Core
 export { generateCreature, calculateStats, getCreatureName, recalculateLevel, getActiveCreature, getTotalEV } from './core/creature'
 export { determineGender, getGenderSymbol } from './core/gender'