Text to list converter

This is the small conversion that sits between every two systems that disagree about how a list is written. A spreadsheet gives you a column, an API wants a comma string; a config file has a comma string, a form wants one per line. Doing it by hand works and stops working at about twenty items.

Each item is trimmed as it converts, which matters because a, b, c split naively on the comma gives b and c with leading spaces. Those spaces are invisible and cause exactly the class of bug where a value looks right and does not match — a lookup fails, a filter returns nothing, a comparison is false for no visible reason.

What this deliberately does not handle is a comma inside a value. Smith, John is one name and two items to any splitter that does not understand quoting, and there is no way to guess which was meant. If your data has commas inside values it is CSV rather than a comma list, and the CSV tools handle the quoting properly — that distinction is the whole reason CSV has a specification.