flexible summarize_combinations sans excel

[lshpaner]

This update refactors the summarize_all_combinations function to make the data_path and data_name parameters optional.
Users can now generate and inspect all variable combinations directly in memory without needing to save results to disk.

Key Changes

• Made data_path and data_name optional (default=None).
• Added conditional logic to run Excel export only when both parameters are provided.
• Moved the return statement outside the conditional to ensure consistent return values.
• Improved printed output behavior when not exporting.
• Updated the docstring to reflect the new optional parameters and logic.

Impact

This enhancement increases flexibility and efficiency for exploratory analysis workflows.
Users can now preview combination summaries directly in memory or export a formatted Excel file when desired.