Motivation to keep slug in org-roam managed files

org-roam does not care about file named. All it cares about is the ID.

We choose to represent the filename as <timestamp>-<slug>.org.

There is a chance for the filenames to differ from the actual titles eventually. And so there is a minor overhead of syncing them manually: org-roam-name-sync-all helps with this.

Current motivation to keep the slug is to review the identity of a file with ease when exporting a cluster as a website with org-roam-export-with-links. The review is required to check if any private files are exported and take action accordingly.