fix(bottest): set bot in test_process_message before starting session

The test was creating BotRunner::new() without setting a bot, causing
execute_bot_logic to fail with 'No bot configured' and return
response: None. Now calls set_bot(Bot::default()) before the session.

bottest/src/bot/runner.rs

@@ -609,7 +609,9 @@ mod tests {
 
     #[tokio::test]
     async fn test_process_message() {
-        let runner = BotRunner::new();
+        let mut runner = BotRunner::new();
+        let bot = Bot::default();
+        runner.set_bot(bot);
         let customer = Customer::default();
 
         let session_id = runner.start_session(customer).unwrap();