fix: standardize file parameter naming across all tools

- Change `relevant_files` to `files` in debug_issue tool
- Change `reference_files` to `files` in think_deeper tool
- Now all tools consistently use `files` parameter name
- Fix cross-platform test for Windows path separators
- Update README to reflect consistent parameter naming

This improves API consistency and reduces confusion when using different tools.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/test_utils.py

@@ -87,7 +87,9 @@ class TestFileUtils:
         assert "file1.py" in content
         assert "file2.js" in content
         assert "readme.md" in content
-        assert "src/module.py" in content
+        # Handle both forward and backslashes for cross-platform compatibility
+        assert "module.py" in content
+        assert "class Module: pass" in content
         
         # Check content
         assert "print('file1')" in content