Refa: add result to callback for agent tool use. (#9137)

### What problem does this PR solve?


### Type of change

- [x] Refactoring

agent/component/begin.py

@@ -46,4 +46,4 @@ class Begin(UserFillUp):
             self.set_input_value(k, v)
 
     def thoughts(self) -> str:
-        return "☕ Here we go..."
+        return ""