feat: loading skeleton on the library page

The library loader streams its one-shot bundle (also the auth gate), so the
active sub-tab shows a skeleton while it loads — a grid skeleton for the
Collections tab, a row skeleton for Bookmarks/History/Page-tags — instead of
only the global nav bar.

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

frontend/src/routes/library/+page.ts

@@ -26,30 +26,36 @@ export const load: PageLoad = async () => {
         distinctPageTags: [] as Awaited<ReturnType<typeof listMyDistinctPageTags>>,
         error: null as string | null
     };
-    try {
-        const [bookmarks, collections, history, pageTags, distinctPageTags] =
-            await Promise.all([
-                listMyBookmarks(),
-                listMyCollections({ limit: 200 }),
-                listMyReadProgress({ limit: 100 }),
-                listMyPageTags({ limit: 100 }),
-                listMyDistinctPageTags(undefined, 100)
-            ]);
-        return {
-            ...empty,
-            bookmarks: bookmarks.items,
-            collections: collections.items,
-            history: history.items,
-            pageTags: pageTags.items,
-            distinctPageTags
-        };
-    } catch (e) {
-        if (e instanceof ApiError && e.status === 401) {
-            return { ...empty, authenticated: false };
-        }
-        if (e instanceof ApiError) {
-            return { ...empty, error: e.message };
-        }
-        throw e;
-    }
+    // Streamed so the active sub-tab shows a skeleton while the one-shot fetch
+    // (also the auth gate) is in flight.
+    return {
+        result: (async () => {
+            try {
+                const [bookmarks, collections, history, pageTags, distinctPageTags] =
+                    await Promise.all([
+                        listMyBookmarks(),
+                        listMyCollections({ limit: 200 }),
+                        listMyReadProgress({ limit: 100 }),
+                        listMyPageTags({ limit: 100 }),
+                        listMyDistinctPageTags(undefined, 100)
+                    ]);
+                return {
+                    ...empty,
+                    bookmarks: bookmarks.items,
+                    collections: collections.items,
+                    history: history.items,
+                    pageTags: pageTags.items,
+                    distinctPageTags
+                };
+            } catch (e) {
+                if (e instanceof ApiError && e.status === 401) {
+                    return { ...empty, authenticated: false };
+                }
+                if (e instanceof ApiError) {
+                    return { ...empty, error: e.message };
+                }
+                throw e;
+            }
+        })()
+    };
 };