优化: aichat 工具体验补强(切生成会话占位气泡治丢首响应/read_symbol符号级提示/失败引导/审批失败toast) + 修复 WorkflowDagDisplay 崩页与 aiChat i18n 缺key

src/composables/ai/useAiConversations.ts

@@ -11,7 +11,7 @@ import { persistUiState } from './useAiPanel'
 import { setStreaming } from './streamingGuard'
 import { nextMsgId, getConvState, clearConvStreamState, clearLastDelta, startApprovalTimer, clearAllApprovalTimers, switchingConvs, getConvStreamState, setConvCurrentText, notifyConversationChanged } from './aiShared'
 import { t } from '@/i18n/i18n-helpers'
-import type { AiConversationDetail, AiMessage, AiToolCallInfo, ConvId } from '@/api/types'
+import type { AiConversationDetail, AiMessage, AiToolCallInfo, ConvId, MessageId } from '@/api/types'
 
 const appSettings = useAppSettingsStore()
 
@@ -333,6 +333,28 @@ export async function switchConversation(id: string, force = false) {
     state.messages = parseConvMessages(rawMsgs, 'loaded')
     // parse 成功才置 active(保证 active 与 messages 一致)
     state.activeConversationId = id
+    // CSW-P1-4: 切到 round0 进行中的会话时,后端该轮 per_conv 只有 user 消息(assistant 占位
+    // 轮末才入),末条是 user → 流式 currentText 无 assistant 承载(MessageList isLastAi 不命中,
+    // flushCurrentText 遇 user break)整轮回复丢失。补前端占位 assistant 气泡承接 currentText,
+    // 生成完成由 AiCompleted/AiAgentRound 收尾 flushCurrentText 回填 content。
+    // targetGen(非终止三态 generating/stopping/compressed)在上文已算,直接复用;
+    // round0-pending- 前缀防御判重(force 重刷同会话时 parseConvMessages 已整体重建,不叠加)。
+    // 字段满足 AiMessage 必填(id/role/content/timestamp),仅 id 因 branded MessageId 逐字段 cast。
+    const lastMsg = state.messages[state.messages.length - 1]
+    if (
+      targetGen
+      && lastMsg
+      && lastMsg.role === 'user'
+      && !state.messages.some((m) => m.role === 'assistant' && m.id.startsWith('round0-pending-'))
+    ) {
+      state.messages.push({
+        id: `round0-pending-${id}` as MessageId,
+        role: 'assistant',
+        content: '',
+        isError: false,
+        timestamp: Date.now(),
+      })
+    }
   } catch (e) {
     // 历史消息解析/映射失败原仅 state.messages=[] → 切换后空白用户不知原因。
     // 改为推错误气泡提示 + 控制台日志(保留 state.messages 不再清空,避免空白无反馈)。