How a value of type T is rendered in a report.

Specialize this rather than overloading to_text: a specialization that does not match is a compilation error, where a misnamed overload fell back on the byte dump in silence. A type without a specialization keeps the built-in rendering.

The to_text free function this replaces is gone. An overload left behind is reported where it would have been used, rather than ignored in silence.