1.4.0

• Re-indexing now removes documents whose files were deleted from disk, along with their chunks and vectors, so the index stays in sync with the directory.
• This pruning runs by default at the end of Engine.Index; set IndexOptions.KeepMissingFiles to true to retain documents for missing files.
• Added a Cleanup pipeline that pages through stored documents and removes only the ones whose file is confirmed missing, leaving present files and ambiguous stat errors untouched.
• Deletes a document's vectors before its metadata, so an interrupted cleanup cannot strand a document whose vectors are already gone, and a re-run finishes it.
• Added DocumentsFromID and DeleteDocument store methods for both the SQLite and PostgreSQL backends.