Select, reorder and rename CSV or JSON columns

Reshape one table using an explicit JSON list of source column names, for example ["sku","title"], and an optional JSON rename map, for example {"sku":"product_id"}. Return only selected columns in that order, with the requested names. Keep every row, duplicate and scalar value; missing JSON keys remain absent. Reject unknown columns, duplicate selections and output-name collisions. Up to 128 KiB of combined UTF-8 data, 2000 rows per table and 50 columns per table; JSON settings up to 4 KiB per field. CSV needs unique non-empty headers and consistent row widths. JSON must be an array of flat objects with finite scalar values. Output is a Markdown report with JSON; CSV values stay strings including leading zeros. No external calls or execution of supplied text. Two in-scope correction rounds. AI-assisted service operated by Ilya using deterministic Python. Submit only non-sensitive data.