fix(mobile): preserve offline section deletion

Persist and display section removal before best-effort filter cleanup. Unfiltered sections skip filter publication; cleanup failures leave an unreachable preference rather than blocking deletion. Exercise the real section provider and persistent storage while filter preferences are read-only.

Co-authored-by: Carl <acda9e433d19dcd0e6b6840f7f4b98f3a56f1fab98049d444c087019e6d36560@buzz.block.builderlab.xyz>
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>

mobile/lib/features/channels/channel_filter/channel_filter_manager.dart

@@ -100,9 +100,40 @@ class ChannelFilterManager extends ChangeNotifier {
     ChannelFilterMode mode, {
     int? windowSeconds,
     bool removeWindow = false,
+  }) => _save(
+    group,
+    mode,
+    windowSeconds: windowSeconds,
+    removeWindow: removeWindow,
+  );
+
+  /// Best-effort cleanup after local deletion. Section IDs are never reused;
+  /// failure leaves an unreachable preference, never blocks the local action.
+  Future<void> clearDeletedSection(String sectionId) async {
+    final group = 'section:$sectionId';
+    if (store.modeFor(group) == ChannelFilterMode.all &&
+        !(store.toJson()['activeWindowSeconds'] as Map? ?? {}).containsKey(
+          group,
+        )) {
+      return;
+    }
+    await _save(
+      group,
+      ChannelFilterMode.all,
+      removeWindow: true,
+      deletedSection: true,
+    );
+  }
+
+  Future<void> _save(
+    String group,
+    ChannelFilterMode mode, {
+    int? windowSeconds,
+    bool removeWindow = false,
+    bool deletedSection = false,
   }) async {
     if (_disposed || !ready || busy) throw StateError('Filters are read-only');
-    if (isGroupLive?.call(group) == false) {
+    if (!deletedSection && isGroupLive?.call(group) == false) {
       throw StateError('Section no longer exists');
     }
     busy = true;
@@ -118,7 +149,7 @@ class ChannelFilterManager extends ChangeNotifier {
       );
       _notify();
       final fresh = await _read();
-      if (isGroupLive?.call(group) == false) {
+      if (!deletedSection && isGroupLive?.call(group) == false) {
         throw StateError('Section no longer exists');
       }
       final next = fresh.edit(

mobile/lib/features/channels/channel_sections/channel_sections_provider.dart

@@ -104,7 +104,12 @@ class ChannelSectionsNotifier extends Notifier<ChannelSectionsState> {
   void renameSection(String sectionId, String newName) =>
       _manager?.renameSection(sectionId, newName);
 
-  void deleteSection(String sectionId) => _manager?.deleteSection(sectionId);
+  void deleteSection(String sectionId) {
+    final manager = _manager;
+    if (manager == null) return;
+    manager.deleteSection(sectionId);
+    _emitManagerState(manager);
+  }
 
   void moveSectionUp(String sectionId) => _manager?.moveSectionUp(sectionId);
 

mobile/lib/features/channels/channels_page/body.dart

@@ -418,32 +418,25 @@ class _SliverChannelsList extends HookConsumerWidget {
                       ],
                     ),
                   );
-                  if (confirmed == true) {
+                  if (confirmed == true && context.mounted) {
+                    // Local section removal must work without filter-read/write
+                    // authority. Cleanup is optional for this never-reused ID.
+                    ref
+                        .read(channelSectionsProvider.notifier)
+                        .deleteSection(section.id);
                     try {
-                      if (filters == null) {
-                        throw StateError('Filters unavailable');
-                      }
-                      await filters.save(
-                        sectionSortGroupKey(section.id),
-                        ChannelFilterMode.all,
-                        removeWindow: true,
-                      );
+                      await filters?.clearDeletedSection(section.id);
                     } catch (_) {
                       if (context.mounted) {
                         ScaffoldMessenger.of(context).showSnackBar(
                           const SnackBar(
                             content: Text(
-                              'Could not reset the section filter. Retry deleting the section.',
+                              'Section deleted. Its saved filter could not be cleared.',
                             ),
                           ),
                         );
                       }
-                      return;
                     }
-                    if (!context.mounted) return;
-                    ref
-                        .read(channelSectionsProvider.notifier)
-                        .deleteSection(section.id);
                   }
                 },
                 onMoveUp: () => ref

mobile/test/features/channels/channels_page_test.dart

@@ -4460,6 +4460,7 @@ class _CompletedPairingNotifier extends PairingNotifier {
 ChannelFilterManager _filterTestManager({
   ChannelFilterStore? cached,
   bool failPublish = false,
+  VoidCallback? onPublish,
 }) {
   final keys = nostr.Keys.generate();
   final crypto = ChannelSortCrypto(keys.nsec, keys.public);
@@ -4471,6 +4472,7 @@ ChannelFilterManager _filterTestManager({
     cache: (_) {},
     fetch: () async => history,
     publish: (content, at) async {
+      onPublish?.call();
       if (failPublish) throw StateError('rejected');
       history = [
         NostrEvent.fromJson(

mobile/test/features/channels/channels_page_test/filter_feedback_tests.dart

@@ -3,6 +3,76 @@ part of '../channels_page_test.dart';
 void _filterFeedbackTests(
   Widget Function({required List<Override> overrides}) buildTestable,
 ) {
+  testWidgets(
+    'deleting an unfiltered section persists offline without filter publication',
+    (tester) async {
+      SharedPreferences.setMockInitialValues({});
+      final prefs = await SharedPreferences.getInstance();
+      final keys = nostr.Keys.generate();
+      const relayUrl = 'https://offline.example';
+      final storage = ChannelSectionsStorage(prefs);
+      storage.write(
+        keys.public,
+        relayUrl,
+        const ChannelSectionStore(
+          sections: [
+            ChannelSection(id: 'offline', name: 'Offline section', order: 0),
+          ],
+        ),
+      );
+      var publications = 0;
+      final manager = _filterTestManager(onPublish: () => publications++);
+      await tester.pumpWidget(
+        buildTestable(
+          overrides: [
+            channelsProvider.overrideWith(
+              () => _FakeNotifier([
+                Channel(
+                  id: 'channel',
+                  name: 'General',
+                  channelType: 'stream',
+                  visibility: 'open',
+                  description: '',
+                  memberCount: 1,
+                  createdBy: 'pk',
+                  createdAt: DateTime(2025),
+                  isMember: true,
+                ),
+              ]),
+            ),
+            relayConfigProvider.overrideWith(
+              () => _FilterFeedbackConfig(
+                RelayConfig(baseUrl: relayUrl, nsec: keys.nsec),
+              ),
+            ),
+            relaySessionProvider.overrideWith(
+              () => _ReconnectingRelaySession(
+                initialStatus: SessionStatus.disconnected,
+              ),
+            ),
+            savedPrefsProvider.overrideWithValue(prefs),
+            channelFilterProvider.overrideWithValue(manager),
+          ],
+        ),
+      );
+      await tester.pumpAndSettle();
+      expect(manager.ready, isFalse);
+      expect(find.text('Offline section'), findsOneWidget);
+      await tester.tap(find.byKey(const Key('section-menu-offline')));
+      await tester.pumpAndSettle();
+      await tester.ensureVisible(find.text('Delete section'));
+      await tester.tap(find.text('Delete section'));
+      await tester.pumpAndSettle();
+      await tester.tap(find.text('Delete'));
+      await tester.pumpAndSettle();
+      expect(find.text('Offline section'), findsNothing);
+      expect(storage.read(keys.public, relayUrl).sections, isEmpty);
+      expect(publications, 0);
+      await tester.pumpWidget(const SizedBox());
+      manager.dispose();
+    },
+  );
+
   testWidgets('Unreads agrees with highlights in the pre-seed frame', (
     tester,
   ) async {
@@ -77,3 +147,10 @@ void _filterFeedbackTests(
     manager.dispose();
   });
 }
+
+class _FilterFeedbackConfig extends RelayConfigNotifier {
+  _FilterFeedbackConfig(this.config);
+  final RelayConfig config;
+  @override
+  RelayConfig build() => config;
+}