Verify and document what Briefcase does with edited submissions from Central

I believe Briefcase will pull each submission once and any subsequent pulls would skip them. However, if a submission media attachment is updated, that gets updated, I believe.

We should confirm the behavior and document recommended action. For example, if edits are used for a particular project, any Briefcase exports/pushes should be preceded by deleting all local submissions and redoing a clean pull.

No specific file or test is named. First confirm how Briefcase handles repeated pulls of unchanged submissions and updated media attachments, then document the verified behavior and the recommended action for projects using edits, including whether a clean pull requires deleting local submissions.

Written by the indexing model from the issue text.