I have raw trade logs coming from the lighter exchange and saved as comma-separated CSV files. Each record may be only a partial fill, so for a single side and symbol I might see something like “L1 L3 L5 S2 S3 S5.” I want a small, local script that: • Reads the existing CSV (column headers already present) containing multiple symbols. • Groups partial fills by side (L/S) and symbol, sums their sizes, and leaves the original rows intact. • Appends two extra rows per symbol/side showing the net size and a new “status” field set to “closed” when the long and short totals cancel each other out, otherwise “running.” • Exports a fresh CSV that keeps the original trade details plus these aggregated results—ready for further analysis. Please build it in any open-source language that runs on macOS or Linux without paid licenses. Include a quick README with install-run instructions and a sample run reproducing the example above so I can verify everything locally.