refactor: use PageData type for page data assertions

Replaced anonymous object casts with the defined `PageData` type in `app/sitemap.ts` and `app/docs/layout.tsx`.
Removed redundant null-coalescing fallbacks `?? {}` in `app/sitemap.ts` as the `PageData` type supports optional properties and subsequent logic uses optional chaining.
Imported `PageData` in `app/docs/layout.tsx` to maintain type consistency across the codebase.

Co-authored-by: longsizhuo <114939201+longsizhuo@users.noreply.github.com>

Author: google-labs-jules[bot]

app/docs/layout.tsx

@@ -7,6 +7,7 @@ import type { PageTree } from "fumadocs-core/server";
 import { CopyTracking } from "@/app/components/CopyTracking";
 import { DocsPageViewTracker } from "@/app/components/DocsPageViewTracker";
 import { cookies } from "next/headers";
+import { type PageData } from "@/app/types/doc";
 
 type Locale = "zh" | "en";
 type SourcePage = ReturnType<typeof source.getPages>[number];
@@ -77,7 +78,7 @@ function chooseVariant(variants: SourcePage[], locale: Locale): SourcePage {
   const originalMatching = variants.find((p) => {
     const { suffix } = stripLocaleSuffix(p.slugs);
     if (suffix !== null) return false;
-    const lang = (p.data as { lang?: string }).lang;
+    const lang = (p.data as PageData).lang;
     return lang === locale;
   });
   if (originalMatching) return originalMatching;

app/sitemap.ts

@@ -127,8 +127,8 @@ function buildDocsEntry(page: SourcePage): MetadataRoute.Sitemap[number] {
  * @returns {Date | undefined} 解析后的 Date 对象，如果找不到或无效则返回 undefined。
  */
 function extractDateFromPage(page: SourcePage): Date | undefined {
-  // (FIX) 使用我们定义的 PageData 类型，而不是 'as' 一个匿名对象
-  const data = (page.data ?? {}) as PageData;
+  // 使用我们定义的 PageData 类型
+  const data = page.data as PageData;
 
   const candidates: DateLike[] = [
     data?.updatedAt,
@@ -183,8 +183,8 @@ function sanitizeSlugPath(slugs: string[]): string {
  * @returns {boolean} 如果是草稿或隐藏，返回 true。
  */
 function isDraftOrHidden(page: SourcePage): boolean {
-  // [BUILD 修复] 使用我们定义的 PageData 类型来代替 'any'
-  const d = (page.data ?? {}) as PageData;
+  // 使用我们定义的 PageData 类型
+  const d = page.data as PageData;
 
   // 检查顶层或 'frontmatter' 嵌套下的 'draft' 或 'hidden' 标志
   return !!(