Move utils.format_domains call into main pshtt lib

Instead of just doing it in the CLI. Currently, non-CLI uses of pshtt are forced to remember to call the function themselves in order to get the same level of sanitization.

Inspect where the CLI currently calls utils.format_domains and identify the main pshtt library entry point used by non-CLI callers. Compare the sanitized results from both paths, then run the existing test suite to verify that domain formatting is applied consistently outside the CLI as well.

Written by the indexing model from the issue text.