Move system tags between groups, and clearer tag group removal

Improvement

Week of November 6, 2026

Move the Speedy Replier tag to any group. Its page now has a Group picker. Its name still can’t change.
Remove only empty tag groups. A group that still has tags shows how many tags you need to move or delete, and Remove appears once it’s empty.
Tidier tag pages. The list of advocates, conversations, introductions or prospects beside a tag’s form is now the same height as the form, and scrolls inside.