feat: OneNote-style notebooks, text fonts, and page navigation

Add notebook.json containers with multi-member pages, fix PDF text
editing (size/bold/drag/double-tap), index SidecarText in search, and
share keyboard page shortcuts plus a PDF scrubber.

Co-authored-by: Cursor <cursoragent@cursor.com>

test/vault_service_test.dart

@@ -339,4 +339,30 @@ void main() {
       expect(notes.single.title, 'Loose Note');
     });
   });
+
+  group('notebook container (OneNote-style)', () {
+    test('createNotebookContainer writes manifest + blank page', () async {
+      final vault = await makeService();
+      await vault.setVaultRoot(tempDir.path);
+
+      final c = await vault.createNotebookContainer('Linear Algebra');
+      expect(c.title, 'Linear Algebra');
+      expect(c.memberCount, 1);
+
+      final containers = await vault.scanContainers();
+      expect(containers.map((x) => x.folderPath), contains(c.folderPath));
+
+      // Containers are excluded from the single-doc / free-note scans.
+      expect(await vault.scanNotes(), isEmpty);
+      expect(await vault.scanNotebooks(), isEmpty);
+
+      final page = await vault.addBlankPageToContainer(
+        c.folderPath,
+        title: 'Lecture 2',
+      );
+      expect(page.title, 'Lecture 2');
+      final again = await vault.scanContainers();
+      expect(again.single.memberCount, 2);
+    });
+  });
 }