fix(site-builder): re-read saved sections when the library opens

Refs #52

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

craft/src/panels/sections/SectionLibraryModal.test.tsx

@@ -100,4 +100,18 @@ describe('SectionLibraryModal', () => {
     h.act(() => { ($('.section-lib-delete') as HTMLElement).click(); });
     expect(extrasApi.get<any[]>('customSections', [])).toHaveLength(0);
   });
+  test('sections loaded silently after mount (replaceAll) appear in My sections on open', () => {
+    mount();
+    // Mirrors useWhpApi: the project load calls replaceAll, which does not re-render.
+    h.act(() => {
+      extrasApi.replaceAll({
+        customSections: [{
+          id: 'custom-loaded', name: 'Loaded hero', family: 'custom', createdAt: 1,
+          tree: { type: { resolvedName: 'Section' }, props: {} },
+        }],
+      });
+    });
+    h.act(() => openSectionLibrary());
+    expect($$('.section-lib-card').map((c) => c.dataset.sectionId)).toContain('custom-loaded');
+  });
 });

craft/src/panels/sections/SectionLibraryModal.tsx

@@ -66,7 +66,7 @@ export const SectionLibraryModal: React.FC = () => {
   const extras = useProjectExtras();
   const { notify } = useNotices();
   const [version, setVersion] = useState(0);
-  const sections = useSections(version);
+  const sections = useSections(version, open);
   const [family, setFamily] = useState<SectionFamily | null>(null);
   const [q, setQ] = useState('');
   const [saveName, setSaveName] = useState('');

craft/src/sections/catalog.ts

@@ -64,12 +64,13 @@ export function getSections(custom: CustomSection[] = []): SectionDef[] {
 
 /** Built-ins plus the site's own saved sections. Reads extras at render time
  *  (extras are ref-backed; callers that mutate them re-render themselves). */
-export function useSections(version = 0): SectionDef[] {
+export function useSections(version = 0, open = true): SectionDef[] {
   const extras = useProjectExtras();
   return useMemo(
     () => getSections(extras.get<CustomSection[]>(CUSTOM_SECTIONS_KEY, [])),
     // eslint-disable-next-line react-hooks/exhaustive-deps
-    [extras, version],
+    // `open` re-reads after a silent extras.replaceAll (project load) that never re-rendered us.
+    [extras, version, open],
   );
 }