fix(#472): clear per-radio in-memory caches on reconnect

Switching radios showed the previous radio's channel history (including
its outgoing messages) on the new radio. The in-memory caches
_channelMessages, _conversations, and _loadedConversationKeys are keyed
by channel index / contact key, not by radio, and were never cleared on
a switch; a new radio's empty store could not overwrite them
(_loadChannelMessages only writes on a non-empty read). On-disk stores
are already per-radio (device+PSK since #277), so no re-keying or
migration is needed.

Clear the three caches in _resetConnectionHandshakeState (runs at the
start of every connect). loadAllChannelMessages and _loadMessagesForContact
repopulate from the new radio's store. Adds a regression test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/connector/meshcore_connector.dart

@@ -2789,11 +2789,34 @@ class MeshCoreConnector extends ChangeNotifier {
     _selfInfoRetryTimer?.cancel();
     _selfInfoRetryTimer = null;
     _hasReceivedDeviceInfo = false;
+    // Drop the previous radio's in-memory history before a new connection loads
+    // its own. These caches are keyed by channel index / contact key, not by
+    // radio, so without this a radio switch would keep showing the prior
+    // radio's channel and DM history (a new radio's empty store cannot
+    // overwrite them). On-disk stores are already per-radio (device+PSK); this
+    // is purely the runtime cache. Repopulated on connect by
+    // loadAllChannelMessages and _loadMessagesForContact. (#472)
+    _channelMessages.clear();
+    _conversations.clear();
+    _loadedConversationKeys.clear();
     _resetSyncProgressState();
     _bleInitialSyncStarted = false;
     _pathHashByteWidth = 1;
   }
 
+  @visibleForTesting
+  void resetConnectionHandshakeStateForTest() =>
+      _resetConnectionHandshakeState();
+
+  @visibleForTesting
+  Map<int, List<ChannelMessage>> get channelMessagesForTest => _channelMessages;
+
+  @visibleForTesting
+  Map<String, List<Message>> get conversationsForTest => _conversations;
+
+  @visibleForTesting
+  Set<String> get loadedConversationKeysForTest => _loadedConversationKeys;
+
   void _resetSyncProgressState() {
     _pendingInitialChannelSync = false;
     _pendingInitialContactsSync = false;

test/connector/channel_cache_reset_test.dart

@@ -0,0 +1,68 @@
+// #472: switching radios must not show the previous radio's history.
+//
+// The per-radio in-memory caches (_channelMessages, _conversations,
+// _loadedConversationKeys) are keyed by channel index / contact key, not by
+// radio. _resetConnectionHandshakeState() runs at the start of every
+// connection, so it must clear them; otherwise a new radio whose store is empty
+// for a channel cannot overwrite the stale entry and keeps rendering the prior
+// radio's history (including its outgoing messages). On-disk stores are already
+// per-radio (device+PSK), so this is purely the runtime cache.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_open/connector/meshcore_connector.dart';
+import 'package:meshcore_open/models/channel_message.dart';
+import 'package:meshcore_open/storage/prefs_manager.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  setUp(() async {
+    SharedPreferences.setMockInitialValues({});
+    PrefsManager.reset();
+    await PrefsManager.initialize();
+  });
+
+  test(
+    'connection reset clears the previous radio in-memory caches (#472)',
+    () {
+      final connector = MeshCoreConnector();
+
+      // Seed the caches as if a prior radio's history had loaded.
+      connector.channelMessagesForTest[0] = [
+        ChannelMessage(
+          senderName: 'PrevRadio',
+          text: 'history from the other radio',
+          timestamp: DateTime.fromMillisecondsSinceEpoch(1000),
+          isOutgoing: true,
+          status: ChannelMessageStatus.sent,
+        ),
+      ];
+      connector.conversationsForTest['deadbeef00'] = [];
+      connector.loadedConversationKeysForTest.add('deadbeef00');
+
+      expect(connector.channelMessagesForTest, isNotEmpty);
+      expect(connector.conversationsForTest, isNotEmpty);
+      expect(connector.loadedConversationKeysForTest, isNotEmpty);
+
+      // A new connection begins.
+      connector.resetConnectionHandshakeStateForTest();
+
+      expect(
+        connector.channelMessagesForTest,
+        isEmpty,
+        reason: 'channel history cache must be dropped on reconnect',
+      );
+      expect(
+        connector.conversationsForTest,
+        isEmpty,
+        reason: 'DM conversation cache must be dropped on reconnect',
+      );
+      expect(
+        connector.loadedConversationKeysForTest,
+        isEmpty,
+        reason: 'loaded-conversation markers must be dropped so DMs reload',
+      );
+    },
+  );
+}