[codex] improve chapter navigation accessibility

docs/frontend-redesign.md

@@ -82,7 +82,7 @@
 - [x] `/` 精简 landing，`/notebooks` 承接登录后笔记本库
 - [x] `dashboard`、`library` 保留 redirect
 - [x] 「新建笔记本」panel 复用 `CreateNotePanel`
-- [ ] 确认 `FluidBG`/`ParticleBG` 无引用后删除
+- [x] 确认 `FluidBG`/`ParticleBG` 无引用后删除
 
 **P1 · 三栏工作台** ✅ 主体完成
 - [x] `notes/[id]/page.tsx` 收敛到 `NoteWorkspace`
@@ -97,8 +97,8 @@
 - [x] 公开导航不再暴露 `/mm-ablation` 内部实验页入口
 - [x] 移动端 `ChatPanel` 回到内容流，避免 sticky 遮挡正文
 - [ ] 浏览器 smoke：视频播放、seek、分享、导出、QA 轮询、书签同步
-- [ ] a11y：三栏 landmark、章节列表 `aria-current`、Lighthouse a11y ≥ 90
-- [ ] 删除确认无引用的旧视觉组件和 `AskBar`
+- [ ] a11y：三栏 landmark、章节列表 `aria-current`、Lighthouse a11y ≥ 90（章节 `aria-current` 已补齐）
+- [x] 删除确认无引用的旧视觉组件和 `AskBar`
 - 验收：`npx tsc --noEmit` 通过；浏览器 smoke 记录写入 `docs/memory/`
 
 ## 4.1 2026-06-25 二次升级计划：电影感首页 + 品牌系统 + 沉浸式登录
@@ -141,6 +141,7 @@
 - 修复移动端内容优先级：视频不能长期挤占首屏，笔记内容和提问入口要更早出现。
 - 问答入口避免遮挡正文，移动端改成稳定的底部输入或内容流内卡片。
 - 章节抽屉补齐焦点管理、`aria-modal` 语义和关闭后的焦点恢复。
+- 章节列表使用 `aria-current="location"` 标记当前主章节和当前子章节，帮助读屏器理解播放位置。
 - 公开导航不暴露内部实验页，`/mm-ablation` 保留为直接访问或开发入口。（已完成）
 - 继续清理 lint、无效 eslint-disable、废弃组件引用和图片加载 warning。
 

web/components/ChapterNav.tsx

@@ -41,7 +41,7 @@ export default function ChapterNav({ chapters, currentIdx, currentTime, onSeek }
             key={i}
             ref={active ? activeRef : undefined}
             onClick={() => onSeek(ch.start)}
-            aria-current={active ? "true" : undefined}
+            aria-current={active ? "location" : undefined}
             whileTap={{ scale: 0.97 }}
             whileHover={{ y: -1 }}
             className={`relative shrink-0 flex min-h-11 items-center gap-2 pl-2 pr-3 py-2 rounded-2xl text-xs

web/components/ChapterRail.tsx

@@ -59,7 +59,7 @@ export default function ChapterRail({
             <button
               ref={active ? activeRef : undefined}
               onClick={() => onSeek(ch.start)}
-              aria-current={active ? "true" : undefined}
+              aria-current={active ? "location" : undefined}
               className={`relative w-full overflow-hidden rounded-xl px-3 py-2 text-left transition-colors
                           ${showProgress ? "pr-9" : ""}
                           ${active
@@ -107,6 +107,7 @@ export default function ChapterRail({
                     <button
                       key={si}
                       onClick={() => onSeek(sub.start)}
+                      aria-current={subActive ? "location" : undefined}
                       className={`rounded-lg px-2 py-1.5 text-left text-xs leading-snug transition-colors
                                   ${subActive
                                     ? "text-[var(--accent)]"

web/components/__tests__/ChapterNavigation.test.tsx

@@ -0,0 +1,91 @@
+import { cleanup, render, screen, within } from "@testing-library/react";
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+import ChapterNav from "../ChapterNav";
+import ChapterRail from "../ChapterRail";
+import type { Chapter } from "@/lib/types";
+
+vi.mock("framer-motion", () => ({
+  motion: {
+    button: ({
+      children,
+      whileHover: _whileHover,
+      whileTap: _whileTap,
+      ...props
+    }: React.ButtonHTMLAttributes<HTMLButtonElement> & {
+      whileHover?: unknown;
+      whileTap?: unknown;
+    }) => {
+      void _whileHover;
+      void _whileTap;
+      return <button {...props}>{children}</button>;
+    },
+  },
+}));
+
+const chapters: Chapter[] = [
+  {
+    title: "Intro",
+    start: 0,
+    end: 60,
+    indices: [],
+    children: [
+      { title: "Opening", start: 0, end: 20, indices: [] },
+      { title: "Setup", start: 20, end: 60, indices: [] },
+    ],
+  },
+  { title: "Deep dive", start: 60, end: 120, indices: [] },
+];
+
+describe("chapter navigation accessibility", () => {
+  afterEach(() => {
+    cleanup();
+  });
+
+  it("marks the active vertical chapter and child as the current location", () => {
+    window.HTMLElement.prototype.scrollIntoView = vi.fn();
+
+    render(
+      <ChapterRail
+        chapters={chapters}
+        currentIdx={0}
+        currentTime={25}
+        onSeek={() => {}}
+      />
+    );
+
+    expect(screen.getByRole("button", { name: /00:00Intro/ })).toHaveAttribute(
+      "aria-current",
+      "location"
+    );
+    expect(screen.getByRole("button", { name: /00:20Setup/ })).toHaveAttribute(
+      "aria-current",
+      "location"
+    );
+    expect(screen.getByRole("button", { name: /01:00Deep dive/ })).not.toHaveAttribute(
+      "aria-current"
+    );
+  });
+
+  it("marks the active horizontal chapter as the current location", () => {
+    window.HTMLElement.prototype.scrollIntoView = vi.fn();
+
+    render(
+      <ChapterNav
+        chapters={chapters}
+        currentIdx={1}
+        currentTime={80}
+        onSeek={() => {}}
+      />
+    );
+
+    const nav = screen.getByRole("navigation", { name: "章节" });
+    expect(within(nav).getByRole("button", { name: /Deep dive/ })).toHaveAttribute(
+      "aria-current",
+      "location"
+    );
+    expect(within(nav).getByRole("button", { name: /Intro/ })).not.toHaveAttribute(
+      "aria-current"
+    );
+  });
+});