【Critical Bug】Master branch is completely broken: NameError: name 'aggregate_regions_dfs' is not defined

[mmmmmhy-1]

Description

The current master branch (latest commit) is completely unusable. Running the encoder on any spreadsheet instantly crashes with:
NameError: name 'aggregate_regions_dfs' is not defined

Traceback (relevant part):
File ".../Spreadsheet_LLM_Encoder.py", line 129, in spreadsheet_llm_encode
aggregated_formats = aggregate_regions_dfs(sheet, type_nfs_map)
NameError: name 'aggregate_regions_dfs' is not defined

Reproduction steps (100% reproducible)

git clone https://github.com/kingkillery/Spreadsheet_LLM_Encoder.git
cd Spreadsheet_LLM_Encoder
pip install -e .
spreadsheet-llm-encode any_file.xlsx   # → crashes immediately

[kingkillery]

Fixed by #31