feat: 添加 Topic-SubTopic 层级结构与 Accordion 侧边栏

- topics/index.json 重构为嵌套模型（topic → subtopics）
- 侧边栏改为 Accordion 交互：默认折叠、同时只展开一个
- 展开/折叠状态通过 localStorage 持久化
- 更新架构文档同步数据模型变更

Co-Authored-By: Claude Code <noreply@anthropic.com>

docs/architecture.md

@@ -77,20 +77,29 @@ examination/
   "updated": "2026-09-02",
   "topics": [
     {
-      "slug": "gc-jvm",
-      "name": "GC / JVM / 三色标记",
-      "description": "...",
-      "path": "topics/gc-jvm",
-      "stats": {
-        "total": 20,
-        "by_type": { "fill_blank": 10, "single_choice": 10 }
-      }
+      "slug": "qunar-ai-fullstack",
+      "name": "去哪儿 AI 面 — AI 全栈方向",
+      "description": "覆盖 JVM/GC、AI Agent 架构、工具链、幻觉治理等核心考察领域",
+      "subtopics": [
+        {
+          "slug": "gc-jvm",
+          "name": "GC / JVM / 三色标记",
+          "description": "...",
+          "path": "topics/gc-jvm",
+          "stats": { "total": 20, "by_type": { "fill_blank": 10, "single_choice": 10 } }
+        }
+      ]
     }
   ]
 }
 ```
 
-前端加载此文件渲染主题列表，`stats` 字段用于展示题目数量。
+- `topics[]` — 顶层主题列表，每个主题是一个手风琴（Accordion）分区
+  - `slug` / `name` / `description` — 主题标识与展示信息
+  - `subtopics[]` — 子主题列表，隶属于该顶层主题
+    - `path` — 子主题数据目录路径
+    - `stats` — 题目数量统计
+- 前端以 Accordion 形式渲染：默认全部折叠，同时只展开一个
 
 ### 3.2 主题元信息 — `topics/{slug}/meta.json`
 
@@ -240,19 +249,20 @@ examination/
 ├────────────┬─────────────────────────────┤
 │  Sidebar   │  Main Content               │
 │            │                             │
-│  📚 主题   │  ┌─ Tabs ─────────────────┐ │
-│  · gc-jvm  │  │ 全部 | 填空 | 选择 |.. │ │
-│  · ai-so   │  └────────────────────────┘ │
-│  · ai-mm   │  ┌─ Toolbar ──────────────┐ │
-│  · ai-he   │  │ 重置 全部显示 提交全部  │ │
-│  · ai-at   │  └────────────────────────┘ │
+│ ▼ 去哪儿.. │  ┌─ Tabs ─────────────────┐ │
+│   · gc-jvm │  │ 全部 | 填空 | 选择 |.. │ │
+│   · ai-so  │  └────────────────────────┘ │
+│   · ai-mm  │  ┌─ Toolbar ──────────────┐ │
+│ ▶ 其他主题 │  │ 重置 全部显示 提交全部  │ │
+│            │  └────────────────────────┘ │
 │            │  ┌─ Question Card ────────┐ │
-│  ────────  │  │ #1  ★★★               │ │
-│  📥 导入   │  │ 题干 [____]            │ │
+│ ────────   │  │ #1  ★★★               │ │
+│ 📥 导入    │  │ 题干 [____]            │ │
 │            │  │ [检查] [显示答案]       │ │
 │            │  │ 💡 解析...              │ │
 │            │  └────────────────────────┘ │
 └────────────┴─────────────────────────────┘
+  ▼ = 展开中  ▶ = 折叠中（Accordion 模式）
 ```
 
 ### 4.2 数据流
@@ -261,9 +271,9 @@ examination/
 页面加载
   │
   ▼
-fetch topics/index.json ──→ 渲染侧边栏主题列表
+fetch topics/index.json ──→ 渲染侧边栏 Accordion（默认全折叠）
   │
-  │ 用户点击主题
+  │ 用户展开某主题 + 点击子主题
   ▼
 fetch topics/{slug}/meta.json ──→ 获取 question_files 列表
   │
@@ -289,12 +299,13 @@ const QUESTION_TYPES = {
 };
 
 // 应用状态
-let topics = [];            // 从 index.json 加载的主题列表
-let currentTopic = null;    // 当前选中的主题 slug
-let currentQuestions = [];  // 当前主题的所有题目（合并自多个题型文件）
-let answers = {};           // qId → { value, correct, revealed }
-let customQuestions = [];   // 通过导入功能临时添加的题目
-let activeTab = 'all';     // 当前 Tab：'all' 或题型名称
+let topicGroups = [];        // 顶层主题列表（含 subtopics）
+let expandedGroup = null;    // 当前展开的顶层主题 slug（Accordion）
+let currentTopic = null;     // 当前选中的子主题 slug
+let currentQuestions = [];   // 当前子主题的所有题目
+let answers = {};            // qId → { value, correct, revealed }
+let customQuestions = [];    // 通过导入功能临时添加的题目
+let activeTab = 'all';      // 当前 Tab：'all' 或题型名称
 ```
 
 ### 4.4 题型配置与渲染

index.html

@@ -47,8 +47,20 @@ body { font-family: -apple-system, 'Segoe UI', sans-serif; background: var(--bg)
 
 /* Sidebar */
 .sidebar-title { font-size: 13px; color: var(--text2); text-transform: uppercase; letter-spacing: 1px; margin-bottom: 12px; padding: 0 8px; }
-.topic-list { list-style: none; }
-.topic-item { padding: 12px 16px; border-radius: 8px; cursor: pointer; transition: all 0.2s; margin-bottom: 4px; }
+
+/* Accordion */
+.accordion-section { margin-bottom: 4px; }
+.accordion-header { padding: 10px 12px; cursor: pointer; user-select: none; border-radius: 8px; transition: background 0.2s; display: flex; align-items: center; gap: 8px; }
+.accordion-header:hover { background: var(--surface2); }
+.accordion-header .accordion-info { flex: 1; min-width: 0; }
+.accordion-header .accordion-name { font-size: 14px; font-weight: 700; color: var(--text); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
+.accordion-header .accordion-desc { font-size: 11px; color: var(--text2); margin-top: 2px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
+.accordion-header .accordion-chevron { font-size: 11px; color: var(--text2); transition: transform 0.2s; flex-shrink: 0; }
+.accordion-section.expanded .accordion-chevron { transform: rotate(180deg); }
+.accordion-body { list-style: none; overflow: hidden; max-height: 0; opacity: 0; transition: max-height 0.25s ease, opacity 0.2s ease; }
+.accordion-section.expanded .accordion-body { max-height: 2000px; opacity: 1; }
+.accordion-body .topic-item { padding: 10px 12px 10px 24px; }
+.topic-item { padding: 10px 12px; border-radius: 8px; cursor: pointer; transition: all 0.2s; margin-bottom: 2px; }
 .topic-item:hover { background: var(--surface2); }
 .topic-item.active { background: var(--accent); color: white; }
 .topic-item .topic-name { font-size: 14px; font-weight: 600; }
@@ -170,8 +182,7 @@ body { font-family: -apple-system, 'Segoe UI', sans-serif; background: var(--bg)
 
 <div class="app">
   <div class="sidebar">
-    <div class="sidebar-title">📚 主题列表</div>
-    <ul class="topic-list" id="topicList"></ul>
+    <div id="accordionContainer"></div>
     <div class="sidebar-section">
       <button class="import-btn" onclick="openImportModal()">📥 导入题目</button>
     </div>
@@ -215,16 +226,16 @@ const QUESTION_TYPES = {
 };
 
 // ─── State ───
-let topics = [];
-let currentTopic = null;
-let currentQuestions = []; // flattened from all type files
-let answers = {};          // qId -> { value, correct, revealed }
-let customQuestions = [];  // imported
-let activeTab = 'all';     // 'all' or type name
+let topicGroups = [];        // [{slug, name, description, subtopics: [...]}, ...]
+let expandedGroup = null;    // slug of the expanded accordion section
+let currentTopic = null;     // slug of the selected subtopic
+let currentQuestions = [];
+let answers = {};
+let customQuestions = [];
+let activeTab = 'all';
 
 // ─── Init ───
 async function init() {
-  // Theme init
   const saved = localStorage.getItem('theme') || 'dark';
   document.documentElement.dataset.theme = saved;
   updateThemeToggle();
@@ -232,10 +243,11 @@ async function init() {
   try {
     const res = await fetch('topics/index.json');
     const data = await res.json();
-    topics = data.topics || [];
-    renderTopicList();
+    topicGroups = data.topics || [];
+    expandedGroup = localStorage.getItem('expandedGroup') || null;
+    renderAccordion();
   } catch (e) {
-    document.getElementById('topicList').innerHTML = '<li style="color:var(--red);padding:12px;">加载主题列表失败</li>';
+    document.getElementById('accordionContainer').innerHTML = '<div style="color:var(--red);padding:12px;">加载主题列表失败</div>';
   }
 }
 
@@ -253,26 +265,63 @@ function updateThemeToggle() {
   if (btn) btn.textContent = document.documentElement.dataset.theme === 'dark' ? '🌙' : '☀️';
 }
 
-// ─── Topic List ───
-function renderTopicList() {
-  const ul = document.getElementById('topicList');
-  let html = '';
-  topics.forEach(t => {
-    const active = currentTopic === t.slug ? 'active' : '';
-    html += `<li class="topic-item ${active}" onclick="selectTopic('${t.slug}')">
-      <div class="topic-name">${t.name}</div>
-      <div class="topic-desc">${t.description}</div>
-      <div class="topic-stats">${t.stats.total} 题 · ${Object.entries(t.stats.by_type).map(([k,v])=>`${typeLabel(k)} ${v}`).join(' / ')}</div>
-    </li>`;
-  });
-  if (customQuestions.length) {
-    html += `<li class="topic-item ${currentTopic === '__custom__' ? 'active' : ''}" onclick="selectTopic('__custom__')">
-      <div class="topic-name">📥 自定义导入</div>
-      <div class="topic-desc">临时导入的题目</div>
-      <div class="topic-stats">${customQuestions.length} 题</div>
-    </li>`;
+// ─── Accordion ───
+function toggleAccordion(slug) {
+  expandedGroup = expandedGroup === slug ? null : slug;
+  localStorage.setItem('expandedGroup', expandedGroup || '');
+  renderAccordion();
+}
+
+function findSubtopic(slug) {
+  for (const g of topicGroups) {
+    const sub = g.subtopics?.find(s => s.slug === slug);
+    if (sub) return sub;
   }
-  ul.innerHTML = html;
+  return null;
+}
+
+function renderAccordion() {
+  const container = document.getElementById('accordionContainer');
+  let html = '';
+
+  topicGroups.forEach(g => {
+    const expanded = expandedGroup === g.slug;
+    html += `<div class="accordion-section ${expanded ? 'expanded' : ''}">
+      <div class="accordion-header" onclick="toggleAccordion('${g.slug}')">
+        <div class="accordion-info">
+          <div class="accordion-name">${escapeHtml(g.name)}</div>
+          <div class="accordion-desc">${escapeHtml(g.description)}</div>
+        </div>
+        <span class="accordion-chevron">▼</span>
+      </div>
+      <ul class="accordion-body">`;
+
+    (g.subtopics || []).forEach(t => {
+      const active = currentTopic === t.slug ? 'active' : '';
+      html += `<li class="topic-item ${active}" onclick="selectTopic('${t.slug}')">
+        <div class="topic-name">${t.name}</div>
+        <div class="topic-desc">${t.description}</div>
+        <div class="topic-stats">${t.stats.total} 题 · ${Object.entries(t.stats.by_type).map(([k,v])=>`${typeLabel(k)} ${v}`).join(' / ')}</div>
+      </li>`;
+    });
+
+    html += `</ul></div>`;
+  });
+
+  if (customQuestions.length) {
+    const active = currentTopic === '__custom__' ? 'active' : '';
+    html += `<div class="accordion-section expanded">
+      <ul class="accordion-body" style="max-height:2000px;opacity:1;">
+        <li class="topic-item ${active}" onclick="selectTopic('__custom__')">
+          <div class="topic-name">📥 自定义导入</div>
+          <div class="topic-desc">临时导入的题目</div>
+          <div class="topic-stats">${customQuestions.length} 题</div>
+        </li>
+      </ul>
+    </div>`;
+  }
+
+  container.innerHTML = html;
 }
 
 function typeLabel(type) {
@@ -284,7 +333,7 @@ async function selectTopic(slug) {
   currentTopic = slug;
   answers = {};
   activeTab = 'all';
-  renderTopicList();
+  renderAccordion();
 
   if (slug === '__custom__') {
     currentQuestions = customQuestions;
@@ -292,7 +341,7 @@ async function selectTopic(slug) {
     return;
   }
 
-  const topic = topics.find(t => t.slug === slug);
+  const topic = findSubtopic(slug);
   if (!topic) return;
 
   try {
@@ -545,7 +594,7 @@ function doImport() {
     const questions = data.questions || (Array.isArray(data) ? data : [data]);
     customQuestions.push(...questions);
     closeImportModal();
-    renderTopicList();
+    renderAccordion();
     if (currentTopic === '__custom__') selectTopic('__custom__');
     document.getElementById('importText').value = '';
   } catch (e) {

topics/index.json

@@ -3,69 +3,76 @@
   "updated": "2026-09-02",
   "topics": [
     {
-      "slug": "gc-jvm",
-      "name": "GC / JVM / 三色标记",
-      "description": "JVM 堆内存模型、GC 算法、三色标记法、垃圾收集器",
-      "path": "topics/gc-jvm",
-      "stats": {
-        "total": 20,
-        "by_type": {
-          "fill_blank": 10,
-          "single_choice": 10
+      "slug": "qunar-ai-fullstack",
+      "name": "去哪儿 AI 面 — AI 全栈方向",
+      "description": "覆盖 JVM/GC、AI Agent 架构、工具链、幻觉治理等核心考察领域",
+      "subtopics": [
+        {
+          "slug": "gc-jvm",
+          "name": "GC / JVM / 三色标记",
+          "description": "JVM 堆内存模型、GC 算法、三色标记法、垃圾收集器",
+          "path": "topics/gc-jvm",
+          "stats": {
+            "total": 20,
+            "by_type": {
+              "fill_blank": 10,
+              "single_choice": 10
+            }
+          }
+        },
+        {
+          "slug": "ai-structured-output",
+          "name": "AI 结构化输出 / Agent 架构",
+          "description": "结构化输出方法、Agent 模式、受限解码",
+          "path": "topics/ai-structured-output",
+          "stats": {
+            "total": 20,
+            "by_type": {
+              "fill_blank": 10,
+              "single_choice": 10
+            }
+          }
+        },
+        {
+          "slug": "ai-memory",
+          "name": "Agent 记忆管理 / 冲突处理",
+          "description": "记忆分层架构、淘汰策略、冲突检测与消解",
+          "path": "topics/ai-memory",
+          "stats": {
+            "total": 20,
+            "by_type": {
+              "fill_blank": 10,
+              "single_choice": 10
+            }
+          }
+        },
+        {
+          "slug": "ai-hallucination",
+          "name": "AI 幻觉 / 目标评价 / 规范",
+          "description": "幻觉分类、Critic 架构、Context Engineering、评估体系",
+          "path": "topics/ai-hallucination",
+          "stats": {
+            "total": 20,
+            "by_type": {
+              "fill_blank": 10,
+              "single_choice": 10
+            }
+          }
+        },
+        {
+          "slug": "ai-tooling",
+          "name": "AI 工具 / Harness / 综合",
+          "description": "AI 工具选型、Harness 架构、可靠性保障、提效分析",
+          "path": "topics/ai-tooling",
+          "stats": {
+            "total": 20,
+            "by_type": {
+              "fill_blank": 10,
+              "single_choice": 10
+            }
+          }
         }
-      }
-    },
-    {
-      "slug": "ai-structured-output",
-      "name": "AI 结构化输出 / Agent 架构",
-      "description": "结构化输出方法、Agent 模式、受限解码",
-      "path": "topics/ai-structured-output",
-      "stats": {
-        "total": 20,
-        "by_type": {
-          "fill_blank": 10,
-          "single_choice": 10
-        }
-      }
-    },
-    {
-      "slug": "ai-memory",
-      "name": "Agent 记忆管理 / 冲突处理",
-      "description": "记忆分层架构、淘汰策略、冲突检测与消解",
-      "path": "topics/ai-memory",
-      "stats": {
-        "total": 20,
-        "by_type": {
-          "fill_blank": 10,
-          "single_choice": 10
-        }
-      }
-    },
-    {
-      "slug": "ai-hallucination",
-      "name": "AI 幻觉 / 目标评价 / 规范",
-      "description": "幻觉分类、Critic 架构、Context Engineering、评估体系",
-      "path": "topics/ai-hallucination",
-      "stats": {
-        "total": 20,
-        "by_type": {
-          "fill_blank": 10,
-          "single_choice": 10
-        }
-      }
-    },
-    {
-      "slug": "ai-tooling",
-      "name": "AI 工具 / Harness / 综合",
-      "description": "AI 工具选型、Harness 架构、可靠性保障、提效分析",
-      "path": "topics/ai-tooling",
-      "stats": {
-        "total": 20,
-        "by_type": {
-          "fill_blank": 10,
-          "single_choice": 10
-        }
-      }
+      ]
     }
   ]
-}
+}