重构: aichat agent 能力系统化(L1元能力+L2/L3后端+list去重)

L1 agent 元能力层(治痛①死循环零交付):
- env_profile 环境姿势注入 + shell 默认 PowerShell(防引号地狱)
- 断路器:同类工具失败≥3熔断 + guard.reset
- detect_environment 主动探测工具(python/node/shell)
- 求助协议 AiHelpRequired 事件 + 前端求助卡

L2 统一状态机后端(治痛②,前端批2):
- ConvState enum 5态 + 合法转换守卫(conv_state.rs)
- GeneratingGuard 接入视图层(guard.rs)

L3 事件总线后端骨架(治痛③④⑤,接入批2):
- EventBus pub-sub + AiBusEvent 8变体(event_bus.rs)

list 工具调用重复治理第一步:
- build_system_prompt_with_excluded 去重被@实体 + 清单注明语

src/i18n/en/aiChat.ts

@@ -145,6 +145,9 @@ export default {
     continueLoopFailed: 'Continue failed: {msg}',
     stopLoopFailed: 'Stop failed: {msg}',
 
+    // ── L1 help protocol (aichat experience & agent capability redesign §2.3, 2026-06-21): circuit-breaker help card ──
+    helpRequiredAck: 'Choice noted. Please rephrase your request to try another approach / continue',
+
     // ── F-260619-03 Phase B: path authorization dialog (LLM accessing dir outside whitelist) ──
     dirAuthRequired: 'Path authorization required',
     dirAuthHint: '{tool} wants to access: {path}',