feat(note): rebuild note editor on the pen-first canvas

Notes now use the single performant inking engine (PenCanvas) instead of
the old ink_canvas, per "all note features on the pen-first canvas".

- ink_stroke_adapter: pure InkStroke<->PenStroke bridge (normalize against
  a logical note page; drop non-freehand shapes/text). Round-trip tested.
- pen_palette_widgets: shared M3 ToolButton/PaletteDivider/RoundIconButton
  so PDF + note editors use identical chrome (PenEditorScreen migrated to
  them; its private copies deleted).
- PenNoteScreen: PenCanvas over a white logical page, undo/redo, title,
  save -> Note.strokes (+ local OCR for search). Pressure curve, eraser
  size/mode and palm rejection all inherited from the shared canvas.
- Route home (new/open) + search note hits -> PenNoteScreen; remove the
  now-redundant "Pen Canvas (beta)" spike button; delete the dead old
  note_editor_screen.

Tests: ink_stroke_adapter (5) + pen_note_screen widget (load + commit, 2).
flutter analyze: 0 issues. Full suite: 265/265.

lib/screens/home_screen.dart

@@ -7,10 +7,9 @@ import '../providers/document_provider.dart';
 import '../providers/note_provider.dart';
 import '../providers/ocr_provider.dart';
 import '../editor/canvas/pen_editor_screen.dart';
-import '../editor/pdf/spike_launcher.dart';
 import '../services/pdf_service.dart';
 import '../services/pptx_service.dart';
-import 'note_editor_screen.dart';
+import '../editor/canvas/pen_note_screen.dart';
 import 'ppt_annotator_screen.dart';
 import 'search_screen.dart';
 import 'settings_screen.dart';
@@ -70,12 +69,6 @@ class HomeScreen extends ConsumerWidget {
               ).push(MaterialPageRoute(builder: (_) => const SearchScreen()));
             },
           ),
-          // New pen-first canvas editor (beta).
-          IconButton(
-            icon: const Icon(Icons.draw_outlined),
-            tooltip: l.penCanvasBeta,
-            onPressed: () => openM1Spike(context),
-          ),
         ],
       ),
       floatingActionButton: FloatingActionButton(
@@ -196,7 +189,7 @@ class HomeScreen extends ConsumerWidget {
     if (context.mounted) {
       Navigator.of(
         context,
-      ).push(MaterialPageRoute(builder: (_) => NoteEditorScreen(note: note)));
+      ).push(MaterialPageRoute(builder: (_) => PenNoteScreen(note: note)));
     }
   }
 
@@ -375,7 +368,7 @@ class _NoteTileState extends ConsumerState<_NoteTile> {
           ),
           onTap: () {
             Navigator.of(context).push(
-              MaterialPageRoute(builder: (_) => NoteEditorScreen(note: note)),
+              MaterialPageRoute(builder: (_) => PenNoteScreen(note: note)),
             );
           },
           onLongPress: () => _confirmDelete(context),
@@ -425,7 +418,7 @@ class _NoteTileState extends ConsumerState<_NoteTile> {
     if (!mounted) return;
     if (result == 'open') {
       Navigator.of(this.context).push(
-        MaterialPageRoute(builder: (_) => NoteEditorScreen(note: widget.note)),
+        MaterialPageRoute(builder: (_) => PenNoteScreen(note: widget.note)),
       );
     } else if (result == 'delete') {
       _confirmDelete(this.context);

lib/screens/note_editor_screen.dart

@@ -1,303 +0,0 @@
-import 'package:flutter/material.dart';
-import 'package:flutter/services.dart' hide UndoManager;
-import 'package:flutter_riverpod/flutter_riverpod.dart';
-
-import '../models/ink_stroke.dart';
-import '../models/note.dart';
-import '../models/pen_tool.dart';
-import '../models/pressure_curve.dart';
-import '../providers/note_provider.dart';
-import '../providers/ocr_provider.dart';
-import '../services/undo_manager.dart';
-import '../utils/stroke_stabilizer.dart';
-import '../widgets/annotation_toolbar.dart';
-import '../widgets/ink_canvas.dart';
-
-class NoteEditorScreen extends ConsumerStatefulWidget {
-  final Note? note;
-
-  const NoteEditorScreen({super.key, this.note});
-
-  @override
-  ConsumerState<NoteEditorScreen> createState() => _NoteEditorScreenState();
-}
-
-class _NoteEditorScreenState extends ConsumerState<NoteEditorScreen> {
-  final UndoManager _undoManager = UndoManager();
-  PenTool _currentTool = PenTool.pen;
-  Color _currentColor = Colors.black;
-  double _currentStrokeWidth = 2.0;
-  bool _filled = false;
-  String _title = 'Untitled';
-  final TextEditingController _titleController = TextEditingController();
-  PressureCurveType _pressureCurveType = PressureCurveType.linear;
-  StabilizationLevel _stabilizationLevel = StabilizationLevel.none;
-  final TransformationController _zoomController = TransformationController();
-  double _zoomLevel = 1.0;
-
-  bool _isDirty = false;
-
-  Note? get _existingNote => widget.note;
-
-  PressureCurve get _pressureCurve {
-    switch (_pressureCurveType) {
-      case PressureCurveType.linear:
-        return PressureCurve.linear;
-      case PressureCurveType.soft:
-        return PressureCurve.soft;
-      case PressureCurveType.hard:
-        return PressureCurve.hard;
-      case PressureCurveType.custom:
-        return const PressureCurve(type: PressureCurveType.custom);
-    }
-  }
-
-  @override
-  void initState() {
-    super.initState();
-    if (_existingNote != null) {
-      _title = _existingNote!.title;
-      for (final stroke in _existingNote!.strokes) {
-        _undoManager.addStroke(stroke);
-      }
-    }
-    _titleController.text = _title;
-  }
-
-  @override
-  void dispose() {
-    _titleController.dispose();
-    _zoomController.dispose();
-    super.dispose();
-  }
-
-  void _onStrokeComplete(InkStroke stroke) {
-    setState(() {
-      _undoManager.addStroke(stroke);
-      _isDirty = true;
-    });
-  }
-
-  void _onErase(String strokeId, List<InkStroke> replacements) {
-    setState(() {
-      final original = _undoManager.currentStrokes
-          .where((s) => s.id == strokeId)
-          .firstOrNull;
-      if (original != null) {
-        _undoManager.removeStroke(original, replacements: replacements);
-        _isDirty = true;
-      }
-    });
-  }
-
-  void _undo() {
-    setState(() {
-      _undoManager.undo();
-      _isDirty = true;
-    });
-  }
-
-  void _redo() {
-    setState(() {
-      _undoManager.redo();
-      _isDirty = true;
-    });
-  }
-
-  Future<void> _save() async {
-    final notifier = ref.read(noteListProvider.notifier);
-    final now = DateTime.now();
-
-    Note savedNote;
-    if (_existingNote != null) {
-      final updated = _existingNote!.copyWith(
-        title: _title,
-        strokes: _undoManager.currentStrokes.toList(),
-        updatedAt: now,
-      );
-      await notifier.updateNote(updated);
-      savedNote = updated;
-    } else {
-      final note = await notifier.createNote(title: _title);
-      final updated = note.copyWith(
-        strokes: _undoManager.currentStrokes.toList(),
-      );
-      await notifier.updateNote(updated);
-      savedNote = updated;
-    }
-
-    if (!mounted) return;
-    setState(() {
-      _isDirty = false;
-    });
-
-    _runLocalOcr(savedNote);
-  }
-
-  /// Run local OCR and index results for search.
-  void _runLocalOcr(Note note) {
-    final noteId = note.id;
-    ref.read(ocrStatusProvider.notifier).state = {
-      ...ref.read(ocrStatusProvider),
-      noteId: OcrStatus.processing,
-    };
-
-    ref
-        .read(ocrServiceProvider)
-        .processNote(note)
-        .then((_) {
-          if (!mounted) return;
-          ref.read(ocrStatusProvider.notifier).state = {
-            ...ref.read(ocrStatusProvider),
-            noteId: OcrStatus.done,
-          };
-        })
-        .catchError((_) {
-          if (!mounted) return;
-          ref.read(ocrStatusProvider.notifier).state = {
-            ...ref.read(ocrStatusProvider),
-            noteId: OcrStatus.failed,
-          };
-        });
-  }
-
-  void _zoomIn() {
-    final newLevel = (_zoomLevel + 0.25).clamp(0.5, 5.0);
-    _applyZoom(newLevel);
-  }
-
-  void _zoomOut() {
-    final newLevel = (_zoomLevel - 0.25).clamp(0.5, 5.0);
-    _applyZoom(newLevel);
-  }
-
-  void _zoomReset() {
-    _applyZoom(1.0);
-  }
-
-  void _applyZoom(double level) {
-    setState(() => _zoomLevel = level);
-    _zoomController.value = Matrix4.diagonal3Values(level, level, 1.0);
-  }
-
-  Future<void> _saveAndNotify() async {
-    await _save();
-    if (!mounted) return;
-    ScaffoldMessenger.of(
-      context,
-    ).showSnackBar(const SnackBar(content: Text('Saved')));
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return PopScope(
-      canPop: true,
-      onPopInvokedWithResult: (didPop, _) {
-        if (didPop && _isDirty) _save();
-      },
-      child: CallbackShortcuts(
-        bindings: {
-          const SingleActivator(LogicalKeyboardKey.keyZ, control: true): _undo,
-          const SingleActivator(LogicalKeyboardKey.keyY, control: true): _redo,
-          const SingleActivator(
-            LogicalKeyboardKey.keyZ,
-            control: true,
-            shift: true,
-          ): _redo,
-          SingleActivator(LogicalKeyboardKey.keyS, control: true):
-              _saveAndNotify,
-        },
-        child: Focus(
-          autofocus: true,
-          child: Scaffold(
-            appBar: AppBar(
-              title: SizedBox(
-                height: 40,
-                child: TextField(
-                  controller: _titleController,
-                  style: const TextStyle(
-                    fontSize: 18,
-                    fontWeight: FontWeight.w600,
-                  ),
-                  decoration: InputDecoration(
-                    border: InputBorder.none,
-                    hintText: 'Note title...',
-                    contentPadding: const EdgeInsets.symmetric(vertical: 8),
-                    suffix: _isDirty
-                        ? const Text(
-                            ' •',
-                            style: TextStyle(
-                              fontWeight: FontWeight.bold,
-                              fontSize: 18,
-                            ),
-                          )
-                        : null,
-                  ),
-                  onChanged: (value) {
-                    _title = value;
-                    setState(() => _isDirty = true);
-                  },
-                ),
-              ),
-              actions: [
-                IconButton(
-                  icon: const Icon(Icons.check),
-                  tooltip: 'Save',
-                  onPressed: _saveAndNotify,
-                ),
-              ],
-            ),
-            body: Column(
-              children: [
-                AnnotationToolbar(
-                  currentTool: _currentTool,
-                  currentColor: _currentColor,
-                  currentStrokeWidth: _currentStrokeWidth,
-                  filled: _filled,
-                  pressureCurveType: _pressureCurveType,
-                  stabilizationLevel: _stabilizationLevel,
-                  canUndo: _undoManager.canUndo,
-                  canRedo: _undoManager.canRedo,
-                  onToolChanged: (tool) => setState(() => _currentTool = tool),
-                  onColorChanged: (color) =>
-                      setState(() => _currentColor = color),
-                  onStrokeWidthChanged: (w) =>
-                      setState(() => _currentStrokeWidth = w),
-                  onFilledChanged: (f) => setState(() => _filled = f),
-                  onPressureCurveChanged: (v) =>
-                      setState(() => _pressureCurveType = v),
-                  onStabilizationChanged: (v) =>
-                      setState(() => _stabilizationLevel = v),
-                  onUndo: _undo,
-                  onRedo: _redo,
-                  onZoomIn: _zoomIn,
-                  onZoomOut: _zoomOut,
-                  onZoomFitWidth: _zoomReset,
-                  zoomLabel: '${(_zoomLevel * 100).round()}%',
-                ),
-                Expanded(
-                  child: InteractiveViewer(
-                    transformationController: _zoomController,
-                    minScale: 0.5,
-                    maxScale: 5.0,
-                    child: InkCanvas(
-                      strokes: _undoManager.currentStrokes,
-                      onStrokeComplete: _onStrokeComplete,
-                      onErase: _onErase,
-                      tool: _currentTool,
-                      color: _currentColor,
-                      strokeWidth: _currentStrokeWidth,
-                      pressureCurve: _pressureCurve,
-                      stabilizationLevel: _stabilizationLevel,
-                      filled: _filled,
-                    ),
-                  ),
-                ),
-              ],
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-}

lib/screens/search_screen.dart

@@ -7,7 +7,7 @@ import '../editor/canvas/pen_editor_screen.dart';
 import '../l10n/app_localizations.dart';
 import '../models/note.dart';
 import '../providers/search_provider.dart';
-import 'note_editor_screen.dart';
+import '../editor/canvas/pen_note_screen.dart';
 
 class SearchScreen extends ConsumerStatefulWidget {
   const SearchScreen({super.key});
@@ -179,7 +179,7 @@ class _NoteSearchResultTile extends StatelessWidget {
       onTap: () {
         Navigator.of(
           context,
-        ).push(MaterialPageRoute(builder: (_) => NoteEditorScreen(note: note)));
+        ).push(MaterialPageRoute(builder: (_) => PenNoteScreen(note: note)));
       },
     );
   }