修阅读'一直载入中'：novel.md gzip + 章节索引 + loading 状态

问题定位：
- novel.md 285KB 线上 Content-Type 被 nginx 默认识别为 application/octet-stream，gzip_types 无法命中，未压缩直传
- 用户网络慢时全本下载数秒甚至更久，一直'载入中 …'
- 附带问题：renderNovel 的 sections forEach idx 和 CHAPTERS 数组错位——'终章之后·当世界再次变聪明'这个非章节 ## heading 被 skip 掉后，之后所有第二部章节的 CHAPTERS[idx] 索引都偏移一位，映射到错误的章节图（不崩溃但显示错）

修复：
1. Dockerfile nginx conf 加 location = /novel.md 用 default_type 'text/markdown; charset=utf-8'，覆盖默认 octet-stream，让 gzip_types 命中。gzip_comp_level 6 / gzip_min_length 512 / gzip_vary on。预计 285KB → ~90KB
2. renderNovel 里 ch 的解析从 CHAPTERS[idx] 改为 CHAPTERS.find(c => c.n === chN)，按语义 n 精确匹配（主部 1-20 + 0 终章 / 第二部 -1 到 -8）。不再受 section 索引漂移影响
3. loadNovel 细化 loading 文案'正在下载全本 …' → '正在渲染章节 …'；await setTimeout(0) 让浏览器先 paint；失败时补兜底直链'直接打开 novel.md'
4. imgPath 从 './images/${ch.img}' 加防守 (ch && ch.img)，第二部 img=null 的章节不渲染 broken img src

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.memory/worklog.json

@@ -489,6 +489,13 @@
       "message": "auto-save 2026-04-18 15:40 (~1)",
       "hash": "d46152c",
       "files_changed": 1
+    },
+    {
+      "ts": "2026-04-18T15:48:56+08:00",
+      "type": "commit",
+      "message": "auto-save 2026-04-18 15:48 (~2)",
+      "hash": "15b2812",
+      "files_changed": 2
     }
   ]
 }

web/Dockerfile

@@ -2,24 +2,7 @@ FROM nginx:alpine
 
 COPY . /usr/share/nginx/html/
 
-RUN printf 'types {\n\
-    text/html                             html htm;\n\
-    text/css                              css;\n\
-    text/plain                            txt;\n\
-    text/markdown                         md;\n\
-    application/javascript                js;\n\
-    application/json                      json;\n\
-    image/jpeg                            jpg jpeg;\n\
-    image/png                             png;\n\
-    image/webp                            webp;\n\
-    image/svg+xml                         svg;\n\
-    image/x-icon                          ico;\n\
-    font/woff                             woff;\n\
-    font/woff2                            woff2;\n\
-}\n\
-default_type application/octet-stream;\n\
-\n\
-server {\n\
+RUN printf 'server {\n\
     listen 80;\n\
     server_name _;\n\
     root /usr/share/nginx/html;\n\
@@ -33,7 +16,13 @@ server {\n\
         access_log off;\n\
     }\n\
 \n\
-    # html / md: always revalidate\n\
+    # novel.md specifically — force text/markdown so gzip triggers\n\
+    location = /novel.md {\n\
+        default_type "text/markdown; charset=utf-8";\n\
+        add_header Cache-Control "public, max-age=0, must-revalidate";\n\
+    }\n\
+\n\
+    # html / md catch-all: always revalidate\n\
     location ~* \\.(html|md)$ {\n\
         add_header Cache-Control "public, max-age=0, must-revalidate";\n\
     }\n\

web/index.html

@@ -922,13 +922,21 @@ function closeLightbox() {
 }
 
 async function loadNovel() {
+  const container = document.getElementById('reader-content');
   try {
-    const resp = await fetch('./novel.md');
+    container.innerHTML = '<div class="loading">正在下载全本 …</div>';
+    const resp = await fetch('./novel.md', { cache: 'no-cache' });
+    if (!resp.ok) throw new Error('HTTP ' + resp.status);
+    container.innerHTML = '<div class="loading">正在渲染章节 …</div>';
     const text = await resp.text();
+    // Yield to the browser so the loading message paints before heavy work
+    await new Promise(r => setTimeout(r, 0));
     renderNovel(text);
   } catch (e) {
-    document.getElementById('reader-content').innerHTML =
-      '<div class="loading" style="color: var(--red)">小说载入失败：' + e.message + '</div>';
+    console.error('loadNovel failed:', e);
+    container.innerHTML =
+      '<div class="loading" style="color: var(--red)">小说载入失败：' + e.message +
+      '。<a href="./novel.md" style="color: var(--gold); text-decoration: underline;">直接打开 novel.md</a></div>';
   }
 }
 
@@ -944,24 +952,28 @@ function renderNovel(md) {
     let m = heading.match(/^(第(\d+)章|终章)\s+(.+)$/);
     let isPart2 = false;
     let num, title;
+    const cnMap = { '一': '01', '二': '02', '三': '03', '四': '04', '五': '05', '六': '06', '七': '07', '八': '08', '九': '09', '十': '10' };
+    const cnToInt = { '一':1,'二':2,'三':3,'四':4,'五':5,'六':6,'七':7,'八':8,'九':9,'十':10 };
+    let kicker, chN;
     if (m) {
       const isEpilogue = !m[2];
       num = isEpilogue ? '终' : m[2].padStart(2, '0');
       title = m[3];
-      // kicker assigned below
-      var kicker = isEpilogue ? 'EPILOGUE' : 'CHAPTER ' + num;
+      kicker = isEpilogue ? 'EPILOGUE' : 'CHAPTER ' + num;
+      chN = isEpilogue ? 0 : parseInt(m[2]);
     } else {
       const m2 = heading.match(/^第二部\s*·\s*第(.+?)章\s*·\s*(.+)$/);
       if (!m2) return;
       isPart2 = true;
-      const cnMap = { '一': '01', '二': '02', '三': '03', '四': '04', '五': '05', '六': '06', '七': '07', '八': '08', '九': '09', '十': '10' };
       const arabic = cnMap[m2[1]] || m2[1];
       num = 'II · ' + arabic;
       title = m2[2];
-      var kicker = 'PART II · CHAPTER ' + arabic;
+      kicker = 'PART II · CHAPTER ' + arabic;
+      chN = -(cnToInt[m2[1]] || parseInt(m2[1]));  // -1 = Part II Ch1, -2 = Part II Ch2, ...
     }
-    const ch = CHAPTERS[idx];
-    const imgPath = ch ? `./images/${ch.img}` : '';
+    // Match chapter by semantic n (immune to section index drift caused by non-chapter ## headings)
+    const ch = CHAPTERS.find(c => c.n === chN);
+    const imgPath = (ch && ch.img) ? `./images/${ch.img}` : '';
     const paragraphs = body.split(/\n\s*\n/).map(p => {
       const line = p.trim();
       if (!line) return '';