xray is a read-only profiler for tabular data: a single streaming pass over a
CSV or DSV file that reports what the file is (shape, delimiter, encoding),
what each column holds (type, fill, cardinality), and what is likely to bite a
later step -- ragged rows, currency text, mixed types or buried headers.

Values stay stringly-typed, so leading zeros and long identifiers are still
text.  It observes only, and never writes.