feat(ux): M1/M2 移动端可用 — 导航汉堡抽屉 + 写作工具条不溢出

M1 左导航响应式抽屉：抽出 lib/nav/items.ts（条目数据+激活判定，纯逻辑+vitest）
共用于桌面静态侧栏（hidden lg:block）与移动汉堡抽屉。新增通用 Drawer（遮罩/
Esc 关闭/打开聚焦，复用 CommandPalette a11y 模式）+ NavDrawer + NavItems；
LeftNav 改 <lg 隐藏，AppShell 顶栏加汉堡（aria-label 打开导航）。

M2 写作工具条不溢出 + 移动端可达章节/助手：Toolbar 改 flex-wrap，390px 不再
横切「尚未保存」；ChapterList/ChapterAssistant 抽出 *Content，Workbench 经
左/右 Drawer 在 <lg 触达目录/助手。

实景 390px 复验（browse）：汉堡显示/静态导航隐藏/抽屉开合聚焦+Esc、工具条
两行不溢出、助手抽屉真注入面板。门禁：lint/typecheck 干净 · vitest 177 · build OK。

apps/web/lib/nav/items.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  GLOBAL_NAV_ITEMS,
+  isNavItemActive,
+  projectNavItems,
+  type NavItem,
+} from "./items";
+
+const PID = "p1";
+
+describe("projectNavItems", () => {
+  it("builds the eight project entries scoped to the project id", () => {
+    const items = projectNavItems(PID);
+
+    expect(items).toHaveLength(8);
+    expect(items.map((i) => i.key)).toEqual([
+      "write",
+      "outline",
+      "foreshadow",
+      "review",
+      "style",
+      "codex",
+      "rules",
+      "skills",
+    ]);
+    expect(items.every((i) => i.href.startsWith(`/projects/${PID}/`))).toBe(
+      true,
+    );
+  });
+});
+
+describe("isNavItemActive", () => {
+  const write: NavItem = {
+    href: `/projects/${PID}/write`,
+    label: "写作",
+    key: "write",
+  };
+
+  it("matches a project item by its activeNav key regardless of pathname", () => {
+    expect(
+      isNavItemActive(write, { pathname: "/anything", activeNav: "write" }),
+    ).toBe(true);
+  });
+
+  it("matches a project item by exact pathname when no activeNav given", () => {
+    expect(isNavItemActive(write, { pathname: `/projects/${PID}/write` })).toBe(
+      true,
+    );
+  });
+
+  it("does not match a project item when neither key nor path align", () => {
+    expect(isNavItemActive(write, { pathname: "/", activeNav: "outline" })).toBe(
+      false,
+    );
+  });
+
+  it("matches a global item by exact pathname only", () => {
+    const works = GLOBAL_NAV_ITEMS[0];
+    expect(isNavItemActive(works, { pathname: "/" })).toBe(true);
+    expect(isNavItemActive(works, { pathname: "/projects/p1/write" })).toBe(
+      false,
+    );
+  });
+
+  it("ignores activeNav for global items (no key)", () => {
+    const settings = GLOBAL_NAV_ITEMS[1];
+    expect(
+      isNavItemActive(settings, { pathname: "/", activeNav: "write" }),
+    ).toBe(false);
+  });
+});

apps/web/lib/nav/items.ts

@@ -0,0 +1,55 @@
+// 左导航条目数据 + 激活判定（纯逻辑，供桌面静态侧栏 / 移动抽屉共用，UX §5.1/§3.1）。
+// 组件只负责渲染；条目与高亮规则在此集中，避免侧栏与抽屉漂移。
+
+export type ActiveNav =
+  | "write"
+  | "outline"
+  | "foreshadow"
+  | "review"
+  | "style"
+  | "codex"
+  | "rules"
+  | "skills";
+
+export interface NavItem {
+  href: string;
+  label: string;
+  // 项目级入口的激活键（与 activeNav 比对高亮）；全局项无 key。
+  key?: ActiveNav;
+}
+
+export const GLOBAL_NAV_ITEMS: readonly NavItem[] = [
+  { href: "/", label: "作品库" },
+  { href: "/settings/providers", label: "设置" },
+];
+
+// 项目内页展开的项目级入口（UX §3.1）。
+export function projectNavItems(projectId: string): NavItem[] {
+  return [
+    { href: `/projects/${projectId}/write`, label: "写作", key: "write" },
+    { href: `/projects/${projectId}/outline`, label: "大纲", key: "outline" },
+    {
+      href: `/projects/${projectId}/foreshadow`,
+      label: "伏笔",
+      key: "foreshadow",
+    },
+    { href: `/projects/${projectId}/review`, label: "审稿", key: "review" },
+    { href: `/projects/${projectId}/style`, label: "文风", key: "style" },
+    { href: `/projects/${projectId}/codex`, label: "设定库", key: "codex" },
+    { href: `/projects/${projectId}/rules`, label: "规则", key: "rules" },
+    { href: `/projects/${projectId}/skills`, label: "技能库", key: "skills" },
+  ];
+}
+
+export interface NavActiveContext {
+  pathname: string;
+  activeNav?: ActiveNav;
+}
+
+// 全局项按精确路径匹配；项目项按 activeNav 键匹配（或路径相等兜底）。
+export function isNavItemActive(item: NavItem, ctx: NavActiveContext): boolean {
+  if (item.key !== undefined) {
+    return item.key === ctx.activeNav || ctx.pathname === item.href;
+  }
+  return ctx.pathname === item.href;
+}