SQLite WAL mode writes go to the -wal file, not the main database.
Without an explicit checkpoint before Close(), writes can be stranded
and lost between CLI invocations.
This was causing `bd migrate` to report success but not actually
persist the version update to the database.
Fixes#434🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
b267395d8c