fix: wrap user input in task only in agentic mode (#2636)

lua/avante/llm.lua

@@ -404,6 +404,7 @@ function M.generate_prompts(opts)
     if msg.is_user_submission then
       message = vim.deepcopy(message)
       local content = message.content
+      if Config.mode == "agentic" then
         if type(content) == "string" then
           message.content = "<task>" .. content .. "</task>"
         elseif type(content) == "table" then
@@ -418,6 +419,7 @@ function M.generate_prompts(opts)
           end
         end
       end
+    end
     table.insert(messages, message)
   end