deletion of workspace folder, fire trigger to copy its file names into csv file

A trigger writing to a csv file is a bad idea. triggers on worksite tabels should be avoided at the best of time.

I would create a backup of the projects table, and add new folders to this on a regular basis to act as the backup. Worksite records folderdeletions in Change events as well as documents being removed from a folder, and you can configure the database to record Folder deletions in Document history.  Checking for these change event and copying the relivent additional information to a cs as a asyncronos action would be my recomendation

Hope this helps