* feat: strip hidden text from PR titles and bodies
Remove HTML comments, markdown comments, and zero-width or bidi characters before the model reads PR text, because GitHub does not show them to people. Tell the coordinator when the text hid something, but not for comments that the repository's PR template also has.
* fix: strip Unicode tag characters and other invisible format characters
Tag characters spell invisible ASCII, a known carrier for hidden prompts. The old list covered only zero-width and bidi characters.
* style: format the tag character test
* fix: keep the joiners, soft hyphens and flag tags that normal text needs
Stripping every Cf character counted emoji, Persian words and the England flag
as hidden text, so the coordinator would say a normal PR body hid content.
Kudo Chien
7a0af35c18