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/settings_screen.dart

@@ -8,13 +8,16 @@ import '../l10n/app_localizations.dart';
 import '../models/pen_tool.dart';
 import '../models/pressure_curve.dart';
 import '../providers/settings_provider.dart';
+import '../screens/app_shell.dart' show exportDiagnosticPack;
 import '../services/vault_service.dart';
 import '../services/webdav_sync_service.dart';
 import '../utils/stroke_stabilizer.dart';
 
 /// Material 3 settings screen for BadNote.
 class SettingsScreen extends ConsumerWidget {
-  const SettingsScreen({super.key});
+  const SettingsScreen({super.key, this.embeddedInShell = false});
+
+  final bool embeddedInShell;
 
   void _showColorPicker(
     BuildContext context,
@@ -88,9 +91,22 @@ class SettingsScreen extends ConsumerWidget {
     final colorScheme = Theme.of(context).colorScheme;
 
     return Scaffold(
-      appBar: AppBar(title: Text(AppLocalizations.of(context).settings)),
+      appBar: embeddedInShell
+          ? AppBar(title: Text(AppLocalizations.of(context).settings))
+          : AppBar(title: Text(AppLocalizations.of(context).settings)),
       body: ListView(
         children: [
+          _SectionHeader(
+            title: AppLocalizations.of(context).diagnosticsSection,
+            icon: Icons.bug_report_outlined,
+          ),
+          ListTile(
+            title: Text(AppLocalizations.of(context).diagnosticsExport),
+            subtitle: Text(AppLocalizations.of(context).diagnosticsExportHint),
+            trailing: const Icon(Icons.ios_share),
+            onTap: () => exportDiagnosticPack(context),
+          ),
+          const Divider(),
           _SectionHeader(title: 'Defaults', icon: Icons.tune),
           Padding(
             padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),