feat(web): 前端与后端同步一批（帧壳 turnId / 并行六态与两级分桶 / documents 渲染 / System 键名 / 主人档案分组）

- 帧壳 `turnId` 在 socket 层不再被丢（`lib/ws.ts` 的 dispatchFrame 补 turnId/seq）—— 按路分桶的前提
- 并行帧组接入：`turn_begin` / `steer_ack` / `pending_ack` / `pending_drain` / `pending_full` /
  `chat_duplicate` ⇒ 六态 + 灰态 + `(sessionId, turnId)` 两级分桶；`appendChunk` 不再永远写尾气泡
- 多路忙态：`session_interrupted` 不再无条件当空闲（看 mode/activeTurns）；`stream_end` 不再只按会话过滤
- `documents` 渲染（含 status/chars/truncated 与**逐字中文 reason**）；`turnId` 历史行分组小标
- `System.tsx` 键名改正（真键 HOST/PORT/ADMIN_USERNAME/ADMIN_PASSWORD，避免照抄静默失效）
- 主人档案**按平台分组** + 平台下拉 + 账号候选；**写盘仍展平数组**（后端契约不变）
- 验证：tsc --noEmit ✅、npm run build ✅、22 个前端测试文件全通过（本次新增 3 文件 108 条断言）
- 未做（如实）：握手 history handler 与断线补拉、上行 interrupt 按钮、proactive_message/subagent_result
  等帧落点、文档上传入口与图片预检、voice 管线、System 的 env 读端点

frontend/web/src/lib/useChat.ts

@@ -1,10 +1,10 @@
 import { useCallback, useState } from "react";
-import { chatStream } from "./api";
+import { ApiError, chatStream } from "./api";
 import { connectWs, isWsOpen } from "./ws";
 import { useAppStore } from "../store/useAppStore";
 import { useModeStore } from "../store/useModeStore";
 import { getClientId } from "./client";
-import { now } from "./util";
+import { now, uid } from "./util";
 
 /** Drives one user turn: push the user bubble, blanket a streaming assistant
  *  bubble, trigger the backend loop over REST (`stream:true`), and let the WS
@@ -16,7 +16,7 @@ import { now } from "./util";
  *  renders per that message's mode. We read the current UI mode here and pass it
  *  on the turn so the backend persists it alongside the message (A3). */
 export function useSendChat(): {
-  send: (text: string, image?: string) => Promise<void>;
+  send: (text: string, image?: string, opts?: { parallel?: boolean }) => Promise<void>;
   sending: boolean;
 } {
   const [sending, setSending] = useState(false);
@@ -27,10 +27,12 @@ export function useSendChat(): {
   const appendChunk = useAppStore((s) => s.appendChunk);
   const addTool = useAppStore((s) => s.addTool);
   const appendTaskLog = useAppStore((s) => s.appendTaskLog);
+  const markLocalDelivery = useAppStore((s) => s.markLocalDelivery);
+  const alignDuplicateMessage = useAppStore((s) => s.alignDuplicateMessage);
   const mode = useModeStore((s) => s.mode);
 
   const send = useCallback(
-    async (text: string, image?: string) => {
+    async (text: string, image?: string, opts: { parallel?: boolean } = {}) => {
       const trimmed = text.trim();
       if ((!trimmed && !image) || sending) return;
       setSending(true);
@@ -42,15 +44,41 @@ export function useSendChat(): {
       // Tag this browser's persistent client id onto the optimistic bubbles so the
       // source label shows immediately and matches the persisted turn (design/16 §4.5).
       const clientId = getClientId();
-      addUserMessage(trimmed, undefined, image, clientId);
+      // 幂等键（契约 §4.3）：随上行一起发，服务端判重命中会回 `chat_duplicate` 帧或
+      // `{duplicate:true,messageId}`（REST 面），本端据此把本地气泡对齐到既有 id ——
+      // 重发/双发不会多出一条气泡。
+      const clientMsgId = uid();
+      addUserMessage(trimmed, undefined, image, clientId, clientMsgId);
       beginAssistant(mode, clientId);
 
       try {
-        await chatStream(sessionId, prompt, image, mode);
+        const res = await chatStream(
+          sessionId,
+          prompt,
+          image,
+          mode,
+          clientMsgId,
+          opts.parallel
+        );
+        // 响应面得如实消费（契约 §4.6）：202 排队不是错误。
+        // `pending_ack` 帧是队列深度的真源，这里只做「万一那条帧没到」的兜底标注；
+        // `duplicate` 同理（同一条事实的 REST 面）。
+        if (res.duplicate && res.messageId) {
+          alignDuplicateMessage(clientMsgId, res.messageId, sessionId);
+        } else if (res.queued) {
+          markLocalDelivery("queued");
+        }
       } catch (err: unknown) {
+        endStream();
+        // ⑥ 被拒：`409 chat_busy`（队列满）—— 这不是「触发失败」，气泡要明确说
+        // 「未送达」，让人知道这句话没进去（而不是只看到一行错误日志）。
+        if (err instanceof ApiError && err.code === "chat_busy") {
+          markLocalDelivery("rejected", { rejectReason: "会话正忙：排队已满，这条未送达" });
+          appendTaskLog("main", "[chat_busy] 排队已满，本条未送达\n");
+          return;
+        }
         // Backend loop not wired or gateway unreachable: show the failure inline
         // rather than leaving a permanently-streaming bubble.
-        endStream();
         const msg = err instanceof Error ? err.message : "触发失败";
         appendChunk(`[stream 触发失败] ${msg}`);
         appendTaskLog("main", `[error] ${msg}\n`);
@@ -59,7 +87,7 @@ export function useSendChat(): {
         setSending(false);
       }
     },
-    [sending, sessionId, mode, addUserMessage, beginAssistant, endStream, appendChunk, addTool, appendTaskLog]
+    [sending, sessionId, mode, addUserMessage, beginAssistant, endStream, appendChunk, addTool, appendTaskLog, markLocalDelivery, alignDuplicateMessage]
   );
 
   return { send, sending };