fix: resolve linting issues across multiple files

- Remove unused imports (os, Optional, json, List, sys, MagicMock, DebugIssueTool)
- Remove unused variable assignments (safe_file_name)
- Fix f-strings without placeholders
- Reorder imports in test_live_integration.py

utils/file_utils.py

@@ -5,7 +5,6 @@ File reading utilities with directory support and token management
 import os
 from pathlib import Path
 from typing import List, Optional, Tuple, Set
-import sys
 
 from .token_utils import estimate_tokens, MAX_CONTEXT_TOKENS