fix(ui): 回答不再折叠，次级页侧栏改真链接并补回头像

真机走查第二批：

1. 普通对话的回答，首个 H2 之后的全部内容（带推理的那一半）被
   <details class="answer-detail">「完整分析」默认收起——用户「输出根本
   看不到」。折叠控件与组件文件一并删除，报告层直接渲染进正文。
   技法审计表保留自己的折叠：那是给人核对的证据，不是回复正文。
   product-voice.ts 同步改掉「UI 会折叠」那句，否则模型继续按折叠写。

2. 次级页侧栏点不了头像、头像样式与首页不一致。根因是 R4 的取舍：
   SecondaryShell 共用，但里面挂的是新写的 AppNavRail 而不是 AppSidebar。
   现在 use-nav-rail 也取 avatar，渲染同一个 UserAvatar；页脚改成真链接，
   指向 / —— 账户菜单连着设置弹窗栈，留在那儿，不在这里复制第二份。

3. 「新建对话」整页刷新。原来走 location.assign，现在是 next/link。
   /login 保留硬跳转：它跨鉴权边界，要先存返回目标。

   注意：第一版我改成了 useRouter()，它在 app-router 上下文外会抛
   「invariant expected app router to be mounted」，打红 12 条渲染测试。
   改用 <Link>，静态渲染也安全；折叠态 tooltip 换成原生 title。

测试 3369，fail 仍 31 且与基线逐条一致；四个路由标记不变；
CSS gzip 40,002。

未修：截图里 `## 适合推进 / 需要避开` 被当字面量渲染，是模型输出里
那两个 H2 前面没有换行，属生成层，另记。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0193vBv6w5MV2cifdTUu9H5P

frontend/src/components/app-nav-rail.tsx

@@ -1,5 +1,6 @@
 "use client";
 
+import Link from "next/link";
 import { usePathname } from "next/navigation";
 import { CalendarDays, FileText, Orbit, SquarePen, Star } from "lucide-react";
 import {
@@ -10,13 +11,13 @@ import {
   SidebarGroupContent,
   SidebarHeader,
   SidebarMenu,
-  SidebarMenuButton,
   SidebarMenuItem,
   SidebarRail,
   useSidebar,
 } from "@/components/ui/sidebar";
 import { persistLoginSessionReturn, sessionHref } from "@/lib/chat-session-url";
 import { groupSessionsByRecency } from "@/lib/session-groups";
+import { UserAvatar } from "@/components/user-avatar";
 import { useNavRail, type NavRailSession } from "@/hooks/use-nav-rail";
 
 /**
@@ -47,24 +48,26 @@ export function AppNavRail() {
   const history = sessions.filter((session) => !session.pinned);
   const groups = groupSessionsByRecency(history);
 
-  /* Same navigation the chat sidebar performs when it leaves for one of these
-     pages: a real document load, with the return target stored first. */
-  function go(href: string) {
+  /* Real links, not buttons with a router call. `useRouter()` throws outside an
+     app-router context (it took out twelve render tests), and an <a href> gives
+     client-side navigation for free — clicking 新建对话 from a chart used to
+     reload the whole document. `/login` keeps the hard exit: it crosses an auth
+     boundary and wants the return target persisted first. */
+  function leaveForLogin() {
     persistLoginSessionReturn();
     if (isMobile) setOpenMobile(false);
-    window.location.assign(href);
+  }
+
+  function closeDrawer() {
+    if (isMobile) setOpenMobile(false);
   }
 
   function renderRow(session: NavRailSession) {
     return (
       <SidebarMenuItem key={session.id}>
-        <button
-          className="session-row nav-rail-row"
-          type="button"
-          onClick={() => go(sessionHref("", session.id))}
-        >
+        <Link className="session-row nav-rail-row" href={sessionHref("", session.id)} onClick={closeDrawer}>
           <span className="session-title">{session.title}</span>
-        </button>
+        </Link>
       </SidebarMenuItem>
     );
   }
@@ -78,23 +81,24 @@ export function AppNavRail() {
         </div>
         <SidebarMenu>
           <SidebarMenuItem>
-            <SidebarMenuButton className="new-chat" type="button" tooltip="新对话" onClick={() => go("/")}>
+            <Link className="new-chat" data-sidebar="menu-button" href="/" title="新对话" onClick={closeDrawer}>
               <SquarePen size={18} strokeWidth={1.75} aria-hidden="true" />
               {showExpandedContent ? <span>新建对话</span> : null}
-            </SidebarMenuButton>
+            </Link>
           </SidebarMenuItem>
           {NAV_PAGES.map(({ href, label, icon: Icon }) => (
             <SidebarMenuItem key={href}>
-              <SidebarMenuButton
+              <Link
                 className="report-nav-button"
-                type="button"
-                tooltip={label}
-                isActive={pathname === href || pathname.startsWith(`${href}/`)}
-                onClick={() => go(href)}
+                data-sidebar="menu-button"
+                data-active={pathname === href || pathname.startsWith(`${href}/`)}
+                href={href}
+                title={label}
+                onClick={closeDrawer}
               >
                 <Icon size={18} strokeWidth={1.75} aria-hidden="true" />
                 {showExpandedContent ? <span>{label}</span> : null}
-              </SidebarMenuButton>
+              </Link>
             </SidebarMenuItem>
           ))}
         </SidebarMenu>
@@ -136,22 +140,32 @@ export function AppNavRail() {
 
       <SidebarFooter className="sidebar-footer">
         {signedOut ? (
-          <button className="nav-rail-identity" type="button" onClick={() => go("/login")}>
+          <a className="nav-rail-identity" href="/login" onClick={leaveForLogin}>
             <span className="profile-initial" aria-hidden="true">·</span>
             {showExpandedContent ? <span><b>去登录</b></span> : null}
-          </button>
+          </a>
         ) : (
-          /* Identity only. Account actions live in the chat page's own menu; a
-             second copy here would need the settings dialog stack to come with it. */
-          <div className="nav-rail-identity" aria-label={account ? `${account.name}，余额 ${account.credits} 点` : undefined}>
-            <span className="profile-initial" aria-hidden="true">{account?.initial ?? "·"}</span>
+          /* Draws the same beam avatar the chat sidebar does — the rail used to
+             show only the initial, so the same account wore two different faces
+             depending on which page you were on. It is a real control now: the
+             account menu itself lives on `/` with the settings dialogs behind
+             it, so this goes there rather than growing a second copy. */
+          <Link
+            className="nav-rail-identity"
+            href="/"
+            aria-label={account ? `${account.name}，余额 ${account.credits} 点，打开账户` : "打开账户"}
+            onClick={closeDrawer}
+          >
+            {account?.avatar
+              ? <UserAvatar avatar={account.avatar} size={32} className="profile-avatar" />
+              : <span className="profile-initial" aria-hidden="true">{account?.initial ?? "·"}</span>}
             {showExpandedContent && account ? (
               <>
                 <span><b>{account.name}</b></span>
                 <small>{account.credits} 点</small>
               </>
             ) : null}
-          </div>
+          </Link>
         )}
       </SidebarFooter>
       <SidebarRail />

frontend/src/components/chat-answer-detail.tsx

@@ -1,25 +0,0 @@
-"use client";
-
-import type { ReactNode } from "react";
-
-import { answerDetailCaption } from "@/lib/chat-answer-split";
-
-export function AnswerDetailDisclosure({
-  headings,
-  streaming = false,
-  children,
-}: {
-  readonly headings: readonly string[];
-  readonly streaming?: boolean;
-  readonly children?: ReactNode;
-}) {
-  return (
-    <details className="answer-detail">
-      <summary>
-        完整分析
-        <small>{streaming ? "正在写…" : answerDetailCaption(headings)}</small>
-      </summary>
-      {streaming ? null : <div className="answer-detail-panel">{children}</div>}
-    </details>
-  );
-}

frontend/src/components/chat-message-content.tsx

@@ -2,7 +2,6 @@
 
 import { memo, useEffect, useState, type ReactNode } from "react";
 
-import { AnswerDetailDisclosure } from "@/components/chat-answer-detail";
 import { prefetchOnIdle } from "@/components/chat-chunk-prefetch";
 import { plainParagraphs } from "@/components/chat-message-paragraphs";
 import { TechniqueAuditDisclosure } from "@/components/technique-audit-disclosure";
@@ -139,13 +138,12 @@ export function ChatMessageContent({
             : <StableMarkdownPrefix text={spoken} renderMarkdown={renderMarkdown} />}
         </div>
       ) : null}
-      {report
-        ? (
-          <AnswerDetailDisclosure headings={layers.headings} streaming={streaming}>
-            {reportBody}
-          </AnswerDetailDisclosure>
-        )
-        : foldedAudit}
+      {/* The body used to sit inside a collapsed 完整分析 control: everything
+          from the first H2 down was one click away, so the part of the answer
+          that carries the reasoning was invisible by default. The answer is the
+          product — it renders inline. The technique audit keeps its own
+          disclosure, because that one is evidence for checking, not the reply. */}
+      {report ? <div className="answer-report-body">{reportBody}</div> : foldedAudit}
     </div>
   );
 }