feat: unified shell, diagnostics pack, native Office, sticky board

Make Surface remote debugging and classroom workflows viable: always-on
structured logs with one-click zip export, a single AppShell chrome,
OOXML PPTX/DOCX annotation without LibreOffice, and a first-class sticky
board. Also drop spike/legacy ink widgets and tighten pen feel
(predictor, PenInfoHistory, page-tile layer).

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

lib/screens/app_shell.dart

@@ -0,0 +1,163 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../diagnostics/badnote_log.dart';
+import '../diagnostics/diagnostic_chrome.dart';
+import '../diagnostics/diagnostic_export.dart';
+import '../l10n/app_localizations.dart';
+import '../theme/app_theme.dart';
+import 'board_screen.dart';
+import 'home_screen.dart';
+import 'search_screen.dart';
+import 'settings_screen.dart';
+
+/// Unified product shell — single chrome for library, board, search, settings.
+class AppShell extends ConsumerStatefulWidget {
+  const AppShell({super.key});
+
+  @override
+  ConsumerState<AppShell> createState() => _AppShellState();
+}
+
+class _AppShellState extends ConsumerState<AppShell> {
+  int _index = 0;
+  final _diagKey = GlobalKey<DiagnosticChromeState>();
+
+  @override
+  void initState() {
+    super.initState();
+    BadNoteLog.instance.info(LogSubsystem.shell, 'shell_open');
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final l = AppLocalizations.of(context);
+    final wide = MediaQuery.sizeOf(context).width >= 900;
+
+    final destinations = [
+      _Dest(Icons.menu_book_outlined, Icons.menu_book, l.libraryTab),
+      _Dest(Icons.sticky_note_2_outlined, Icons.sticky_note_2, l.boardTab),
+      _Dest(Icons.search, Icons.search, l.search),
+      _Dest(Icons.tune, Icons.tune, l.settings),
+    ];
+
+    final pages = const [
+      HomeScreen(embeddedInShell: true),
+      BoardScreen(),
+      SearchScreen(embeddedInShell: true),
+      SettingsScreen(embeddedInShell: true),
+    ];
+
+    final body = DiagnosticChrome(
+      key: _diagKey,
+      child: pages[_index],
+    );
+
+    if (wide) {
+      return Scaffold(
+        body: Row(
+          children: [
+            NavigationRail(
+              selectedIndex: _index,
+              onDestinationSelected: _select,
+              extended: MediaQuery.sizeOf(context).width >= 1200,
+              labelType: MediaQuery.sizeOf(context).width >= 1200
+                  ? NavigationRailLabelType.none
+                  : NavigationRailLabelType.all,
+              leading: Padding(
+                padding: const EdgeInsets.only(top: 12, bottom: 24),
+                child: Column(
+                  children: [
+                    Text(
+                      'BadNote',
+                      style: Theme.of(context).textTheme.titleLarge?.copyWith(
+                            color: AppTokens.copper,
+                            fontWeight: FontWeight.w700,
+                          ),
+                    ),
+                    const SizedBox(height: 4),
+                    Text(
+                      l.shellTagline,
+                      style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                            color: AppTokens.inkMuted,
+                          ),
+                    ),
+                  ],
+                ),
+              ),
+              trailing: Expanded(
+                child: Align(
+                  alignment: Alignment.bottomCenter,
+                  child: Padding(
+                    padding: const EdgeInsets.only(bottom: 16),
+                    child: DiagnosticToggleButton(
+                      onToggle: () => _diagKey.currentState?.toggle(),
+                      onExport: () => _diagKey.currentState?.exportPack(),
+                    ),
+                  ),
+                ),
+              ),
+              destinations: [
+                for (final d in destinations)
+                  NavigationRailDestination(
+                    icon: Icon(d.icon),
+                    selectedIcon: Icon(d.selectedIcon),
+                    label: Text(d.label),
+                  ),
+              ],
+            ),
+            VerticalDivider(width: 1, color: AppTokens.rule.withValues(alpha: 0.8)),
+            Expanded(child: body),
+          ],
+        ),
+      );
+    }
+
+    return Scaffold(
+      body: body,
+      bottomNavigationBar: NavigationBar(
+        selectedIndex: _index,
+        onDestinationSelected: _select,
+        destinations: [
+          for (final d in destinations)
+            NavigationDestination(
+              icon: Icon(d.icon),
+              selectedIcon: Icon(d.selectedIcon),
+              label: d.label,
+            ),
+        ],
+      ),
+    );
+  }
+
+  void _select(int i) {
+    BadNoteLog.instance.info(LogSubsystem.shell, 'tab', fields: {'index': i});
+    setState(() => _index = i);
+  }
+}
+
+class _Dest {
+  const _Dest(this.icon, this.selectedIcon, this.label);
+  final IconData icon;
+  final IconData selectedIcon;
+  final String label;
+}
+
+/// Helper used by settings when not embedded — still export packs.
+Future<void> exportDiagnosticPack(BuildContext context) async {
+  try {
+    final result = await DiagnosticExport.instance.exportPack();
+    if (!context.mounted) return;
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(
+        content: Text('诊断包: ${result.zipPath}'),
+        duration: const Duration(seconds: 5),
+      ),
+    );
+  } catch (e) {
+    if (!context.mounted) return;
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(content: Text('导出失败: $e')),
+    );
+  }
+}