Round 2 renamed only MentionDropdown's fixture; three siblings retained
the old suffix. Rename PersonMentionEditor, confirm, and TranscriptionBlock
test hosts to the .test-fixture suffix and update the three importers so
the boundary is uniform across the repo. Felix #1 / Tobi #1 on PR #629.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
