DroppedNestFiles.Select keeps the dropped paths with the .nest extension
in any case, as the WinForms main window does, ignoring everything else.
It returns full paths in the order dropped, each once however its path is
written, compared as NestTabs compares open files. Any says whether the
drop holds a nest file, so a window accepts it only then.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
