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/services/ocr_service.dart

@@ -1,5 +1,6 @@
 import 'dart:io';
 
+import '../diagnostics/badnote_log.dart';
 import '../editor/persistence/sidecar_repository.dart';
 import '../models/note.dart';
 import '../models/pen_tool.dart';
@@ -16,6 +17,10 @@ class OcrService {
   /// working. [note.id] is the synthetic note path, which is exactly the
   /// `sourceFilePath` the editor opened its [SidecarRepository] with.
   Future<void> processNote(Note note) async {
+    BadNoteLog.instance.info(LogSubsystem.diag, 'ocr_start', fields: {
+      'note': note.id,
+      'strokes': note.strokes.length,
+    });
     final parts = <String>[];
 
     for (final stroke in note.strokes) {
@@ -41,12 +46,18 @@ class OcrService {
         final recognized = await OcrEngine.recognizeImage(png);
         if (recognized != null && recognized.isNotEmpty) {
           parts.add(recognized);
+          BadNoteLog.instance.info(LogSubsystem.diag, 'ocr_handwriting', fields: {
+            'chars': recognized.length,
+          });
         }
       }
     }
 
     final combined = parts.join(' ').trim();
-    if (combined.isEmpty) return;
+    if (combined.isEmpty) {
+      BadNoteLog.instance.debug(LogSubsystem.diag, 'ocr_empty');
+      return;
+    }
 
     // Persist into the note's sidecar so the vault-scan search index finds it.
     // Prefer the editor's already-open repo (same in-memory sidecar — no race);