修复: DeepSeek 400 全量扫描 + 队列 per-conv 隔离

- openai_compat: 扫描所有 assistant 消息剥离 orphan tool_calls（原仅查末条）
- queue 加 conversationId 字段，按会话精准 drain
- regenerate/editMessage 只清本会话排队消息
- newConversation 保留旧会话排队消息
- AiError 只清出错会话的队列项

src/components/ai/MessageList.vue

@@ -730,13 +730,13 @@ defineExpose({
           </div>
 
 
-          <!-- token 用量(仅最后一条 AI 消息 + 非流式;ai.ts handleEvent 已按 df-show-token-usage 开关过滤 lastTokenUsage) -->
+          <!-- token 用量(显示在每条 assistant 消息底部,非流式且有数据时) -->
           <div
-            v-if="isLastAi(item.msg) && !store.state.streaming && store.state.lastTokenUsage"
+            v-if="item.msg.role === 'assistant' && !store.state.streaming && item.msg.tokenUsage"
             class="ai-token-usage"
           >
             <span class="ai-token-usage-icon">🔣</span>
-            <span>{{ formatTokens(store.state.lastTokenUsage.prompt) }} in · {{ formatTokens(store.state.lastTokenUsage.completion) }} out</span>
+            <span>{{ formatTokens(item.msg.tokenUsage.prompt) }} in · {{ formatTokens(item.msg.tokenUsage.completion) }} out</span>
           </div>
 
           <!-- 工具调用卡片(渲染/折叠/审批全下沉到 ToolCardList+ToolCard 子组件,MessageList 仅转发审批) -->