Fix CI issues: lint, type checker, and test failures

- Remove unused imports from test and example files
- Fix f-string formatting in examples
- Add proper type handling for Union[str, Dict] in agent_utils.py
- Fix XML parser test assertion to match expected output
- Use isinstance() for proper type narrowing in LLM calls

Co-Authored-By: João <joao@crewai.com>

tests/test_integration_llm_features.py

@@ -1,4 +1,3 @@
-import pytest
 from unittest.mock import Mock, patch
 from crewai import Agent, Task, Crew, LLM
 from crewai.lite_agent import LiteAgent