Fix bugs found in full code audit

- Edit screens (note, task): cache _initFuture in initState instead of
  calling _loadExisting() from FutureBuilder on every rebuild. Prevents
  race condition where multiple concurrent loads could overwrite edits.
  Also removes unnecessary _loaded flag and simplifies the pattern.

- Note editor: remove onChanged: (_) => setState((){}) on the body
  TextField — triggered a full rebuild on every keystroke for no reason.

- SSE streaming: use utf8.decode(chunk, allowMalformed: true) so a
  malformed byte sequence from the server skips rather than throwing an
  unhandled FormatException that escaped all catch blocks.

- Chat provider: guard msgs.isEmpty before accessing msgs.last during
  SSE chunk processing to prevent a potential index error on empty state.

- Offline queue drain: check mounted before and after each async gap in
  _drainQueue so ref is never accessed on a disposed widget.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/app.dart

@@ -245,12 +245,15 @@ class _QuickCaptureBarState extends ConsumerState<_QuickCaptureBar> {
   }
 
   Future<void> _drainQueue() async {
+    if (!mounted) return;
     final queue = ref.read(captureQueueProvider);
     if (queue.isEmpty) return;
     final api = ref.read(quickCaptureApiProvider);
     for (final text in List<String>.from(queue)) {
+      if (!mounted) break;
       try {
         final result = await api.capture(text);
+        if (!mounted) break;
         await ref.read(captureQueueProvider.notifier).dequeue(text);
         switch (result.type) {
           case 'note':
@@ -263,7 +266,7 @@ class _QuickCaptureBarState extends ConsumerState<_QuickCaptureBar> {
         break; // Still offline — stop draining.
       } catch (_) {
         // Server/parse error — remove to avoid infinite retries.
-        await ref.read(captureQueueProvider.notifier).dequeue(text);
+        if (mounted) await ref.read(captureQueueProvider.notifier).dequeue(text);
       }
     }
   }

lib/data/api/chat_api.dart

@@ -92,7 +92,7 @@ class ChatApi {
       String currentEvent = '';
 
       await for (final chunk in stream) {
-        buf.write(utf8.decode(chunk));
+        buf.write(utf8.decode(chunk, allowMalformed: true));
         final raw = buf.toString();
         final lines = raw.split('\n');
 

lib/providers/chat_provider.dart

@@ -90,6 +90,7 @@ class MessagesNotifier extends FamilyAsyncNotifier<List<Message>, int> {
       await for (final chunk in repo.streamGeneration(convId)) {
         streamedContent = true;
         final msgs = state.requireValue;
+        if (msgs.isEmpty) continue;
         final updated = msgs.last.copyWith(content: msgs.last.content + chunk);
         state = AsyncData([...msgs.sublist(0, msgs.length - 1), updated]);
       }

lib/screens/notes/note_edit_screen.dart

@@ -20,7 +20,16 @@ class _NoteEditScreenState extends ConsumerState<NoteEditScreen> {
   final _contentController = TextEditingController();
   bool _preview = false;
   bool _saving = false;
-  bool _loaded = false;
+
+  // Future is created once in initState so FutureBuilder never restarts it.
+  late final Future<void> _initFuture;
+
+  @override
+  void initState() {
+    super.initState();
+    _initFuture =
+        widget.noteId != null ? _loadExisting() : Future.value();
+  }
 
   @override
   void dispose() {
@@ -30,15 +39,10 @@ class _NoteEditScreenState extends ConsumerState<NoteEditScreen> {
   }
 
   Future<void> _loadExisting() async {
-    if (_loaded || widget.noteId == null) {
-      _loaded = true;
-      return;
-    }
     final note =
         await ref.read(notesRepositoryProvider).getOne(widget.noteId!);
     _titleController.text = note.title;
     _contentController.text = note.body;
-    _loaded = true;
   }
 
   Future<void> _delete() async {
@@ -97,7 +101,7 @@ class _NoteEditScreenState extends ConsumerState<NoteEditScreen> {
   @override
   Widget build(BuildContext context) {
     return FutureBuilder(
-      future: _loadExisting(),
+      future: _initFuture,
       builder: (context, snapshot) {
         return Scaffold(
           appBar: AppBar(
@@ -159,7 +163,6 @@ class _NoteEditScreenState extends ConsumerState<NoteEditScreen> {
                                 expands: true,
                                 keyboardType: TextInputType.multiline,
                                 textAlignVertical: TextAlignVertical.top,
-                                onChanged: (_) => setState(() {}),
                               ),
                             ),
                     ),

lib/screens/tasks/task_edit_screen.dart

@@ -23,7 +23,16 @@ class _TaskEditScreenState extends ConsumerState<TaskEditScreen> {
   TaskPriority _priority = TaskPriority.medium;
   DateTime? _dueDate;
   bool _saving = false;
-  bool _loaded = false;
+
+  // Future is created once in initState so FutureBuilder never restarts it.
+  late final Future<void> _initFuture;
+
+  @override
+  void initState() {
+    super.initState();
+    _initFuture =
+        widget.taskId != null ? _loadExisting() : Future.value();
+  }
 
   @override
   void dispose() {
@@ -33,17 +42,13 @@ class _TaskEditScreenState extends ConsumerState<TaskEditScreen> {
   }
 
   Future<void> _loadExisting() async {
-    if (_loaded || widget.taskId == null) {
-      _loaded = true;
-      return;
-    }
-    final task = await ref.read(tasksRepositoryProvider).getOne(widget.taskId!);
+    final task =
+        await ref.read(tasksRepositoryProvider).getOne(widget.taskId!);
     _titleController.text = task.title;
     _descController.text = task.description ?? '';
     _status = task.status;
     _priority = task.priority;
     _dueDate = task.dueDate;
-    _loaded = true;
   }
 
   Future<void> _save() async {
@@ -117,7 +122,7 @@ class _TaskEditScreenState extends ConsumerState<TaskEditScreen> {
   @override
   Widget build(BuildContext context) {
     return FutureBuilder(
-      future: _loadExisting(),
+      future: _initFuture,
       builder: (context, snapshot) {
         return Scaffold(
           appBar: AppBar(