What’s fixed

• A collection served from files is no longer measured against the rows it left behind. Turning one into a folder leaves its old records in place, read by nothing — but nibble:check still held the schema to them, so removing a field from the blueprint stranded rows nobody serves and stopped the site booting. The advice it gave could not be taken either: no migration operation empties a collection the schema still has.
• A refused release leaves the tree as it found it. bin/nibble-release writes the version and the changelog heading before running the checks, so a release that failed them left both files modified with nothing committed or tagged — and the next attempt refused, because Unreleased had already been emptied. It now puts both back on any exit that does not reach the commit.