Data mapping transformer

Every rule runs row by row, in your tab. A value that is missing, empty, or fails its cast falls back to the rule's default and is counted in the facts above, never silently converted. Lookup tables match exact text; a miss either writes the rule's default or leaves the cell empty. The mapping itself is separate from the data: download it and the same rules reshape next month's file. It does not write to databases or APIs; it reshapes rows and nothing more.