All @pdf-testkit/* to 0.1.6 (element-moved, uncharacterized-change,
grouping rules 1-extension + 2b). The action's committed ncc bundle is
rebuilt so the v0.1.6 tag carries the new events in PR comments.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019eLgo72VYmQp3kNz9PZDHs