feat: 顶栏显示当前页名,去掉独立标题行;Logo回首页/页名回顶部

- 新增 PageTitleContext:页面上报标题,顶栏 brand 位显示当前页名(全部资料/
  热门资料/最新/官方/分类名/搜索/我的收藏),未上报则回退品牌名
- AssetStreamPage、Favorites 上报标题;移除资料流内单独的标题行,省出空间
- 顶栏拆分点击:Logo→首页(首页则回顶部);页名文字→回到当前页顶部

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/PageTitleContext.tsx

@@ -0,0 +1,41 @@
+import {
+  createContext,
+  useContext,
+  useEffect,
+  useState,
+  type PropsWithChildren,
+} from "react";
+
+type PageTitleCtx = {
+  title: string | null;
+  setTitle: (title: string | null) => void;
+};
+
+const PageTitleContext = createContext<PageTitleCtx | null>(null);
+
+/**
+ * Lets a page publish its title to the global header so the header can show the
+ * current page name (e.g. "全部资料" / "热门资料") in place of the brand, avoiding
+ * a separate on-page title row. Pages that don't set one fall back to the brand.
+ */
+export function PageTitleProvider({ children }: PropsWithChildren) {
+  const [title, setTitle] = useState<string | null>(null);
+  return (
+    <PageTitleContext.Provider value={{ title, setTitle }}>
+      {children}
+    </PageTitleContext.Provider>
+  );
+}
+
+export function usePageTitle(): string | null {
+  return useContext(PageTitleContext)?.title ?? null;
+}
+
+/** Publish the current page's title; clears it again when the page unmounts. */
+export function useSetPageTitle(title: string | null): void {
+  const setTitle = useContext(PageTitleContext)?.setTitle;
+  useEffect(() => {
+    setTitle?.(title);
+    return () => setTitle?.(null);
+  }, [setTitle, title]);
+}