Convert XLS to JSONL

XLS is the legacy binary spreadsheet format used by Microsoft Excel from 1987 through the Office 2003 era, based on Microsoft's proprietary Binary Interchange File Format (BIFF). It stores worksheets, formulas, charts, and macros in a binary structure that requires Microsoft's format specification to parse correctly. XLS remains common in older enterprise systems and when compatibility with legacy versions of Excel is required.

JSONL (JSON Lines, also known as NDJSON) stores one complete, valid JSON object per line in a plain-text file. This line-by-line structure makes it ideal for streaming large datasets, log files, and machine learning training data, since each record can be processed independently without loading the entire file into memory. JSONL is increasingly standard in data engineering, LLM training pipelines, and high-throughput logging systems.