Combine extract.custom hotfixes for dev

[mborodii-prog]

Summary

Combines the two extract.custom hotfix branches into one PR targeting dev.

Changes

• Preserves list output from extract.custom when the service returns single-column data as a string.
• Keeps explicit single-item output lists as list-style outputs instead of forcing columns output.
• Fixes multi-input/single-output extract.custom merging so per-input match lists are combined into one de-duplicated output list.
• Keeps labeled multi-input output_format: Columns behavior working.

Testing

$env:PYTHONPATH='.'; pytest tests\recipes\wrangles\test_extract.py::TestExtractCustom::test_extract_custom_multi_input_single_output_preserves_match_lists tests\recipes\wrangles\test_extract.py::TestExtractCustom::test_extract_custom_use_labels_output_format_columns_multi_input tests\recipes\wrangles\test_extract.py::TestExtractBrackets::test_extract_brackets_single_item_output_list tests\recipes\wrangles\test_extract.py::TestExtractBrackets::test_extract_brackets_single_item_output_list_no_matches -q

Result: 4 passed.