When bd import finds no changes (0 created, 0 updated), it now updates the database modification timestamp to signal sync validation passed. This fixes 'bd sync' refusing to export with 'JSONL is newer than database' error that occurs after git pull updates JSONL mtime without content changes. Root cause: Import validated DB/JSONL are in sync but didn't update DB mtime, causing timestamp-based sync validation to perpetually fail. Amp-Thread-ID: https://ampcode.com/threads/T-560b9c11-e368-45e6-b1e3-512b6d6010a1 Co-authored-by: Amp <amp@ampcode.com>