refactor: enhance API service to include non-image files in requests and improve chat message synchronization logic

lib/core/services/api_service.dart

@@ -2442,6 +2442,14 @@ class ApiService {
       debugPrint('DEBUG: Including tool_ids in SSE request: $toolIds');
     }
 
+    // Include non-image files at the top level as expected by Open WebUI
+    if (allFiles.isNotEmpty) {
+      data['files'] = allFiles;
+      debugPrint(
+        'DEBUG: Including non-image files in request: ${allFiles.length}',
+      );
+    }
+
     // Don't add session_id or id - they break SSE streaming!
     // The server falls back to task-based async when these are present
 

lib/features/chat/providers/chat_providers.dart

@@ -37,9 +37,15 @@ class ChatMessagesNotifier extends StateNotifier<List<ChatMessage>> {
 
       // Only react when the conversation actually changes
       if (previous?.id == next?.id) {
-        // If same conversation but server updated it (e.g., title/content), sync messages without flicker
+        // If same conversation but server updated it (e.g., title/content), avoid overwriting
+        // locally streamed assistant content with an outdated server copy.
         if (previous?.updatedAt != next?.updatedAt) {
-          state = next?.messages ?? state;
+          final serverMessages = next?.messages ?? const [];
+          // Only replace local messages if the server has strictly more messages
+          // (i.e., includes new content we don't have yet).
+          if (serverMessages.length > state.length) {
+            state = serverMessages;
+          }
         }
         return;
       }