Run the source operators, and report what is covered

### Task Summary

A source reads a file rather than an upstream port, so it is configured from a file the runner writes rather than from a table, and the variants follow the configuration: a CSV with a header and without, an encoding per charset.

Two reports come with it. One prints which operators run and which are withheld and why, so the state of the set is a command rather than a claim. The other parses every generated script and fails on one that a hostile column name would break, which is a whole class of defect a comparison cannot see.

Step 24 of 27 in #8325. It reads the generator trait, so it needs #8327, and the coverage it reports names operators the family steps carry, so it comes after them.