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/l10n/app_localizations_en.dart

@@ -301,6 +301,43 @@ class AppLocalizationsEn extends AppLocalizations {
     return '$current / $total';
   }
 
+  @override
+  String get libraryTab => 'Library';
+
+  @override
+  String get boardTab => 'Stickies';
+
+  @override
+  String get shellTagline => 'Ink · Annotate · Know';
+
+  @override
+  String get notesSection => 'Notes';
+
+  @override
+  String get documentsSection => 'Documents';
+
+  @override
+  String get emptyLibraryTitle => 'Nothing here yet';
+
+  @override
+  String get emptyLibraryBody => 'Create a note, or import PDF / PPT / Word';
+
+  @override
+  String get diagnosticsSection => 'Diagnostics';
+
+  @override
+  String get diagnosticsExport => 'Export diagnostic pack';
+
+  @override
+  String get diagnosticsExportHint =>
+      'Reproduce on Surface, export, and send the zip back';
+
+  @override
+  String get diagnosticsToggle => 'Input diagnostics overlay';
+
+  @override
+  String get penSettingsUnified => 'Pen & ink';
+
   @override
   String get board => 'Board';